Abstract:
A spare tire installation structure for a vehicle has a first rigid member disposed within a trunk compartment of the vehicle, and a second rigid member configured vehicle rearward of the first rigid member and disposed within the trunk compartment of the vehicle. The first rigid member and the second rigid member define a space to house a spare tire. The second rigid member is configured to displace the spare tire vehicle forward and into the first rigid member in response to a rear collision to the vehicle. The first rigid member is configured to split a wheel of the spare tire.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from Japanese Patent Application No. 2009-159874, filed Jul. 6, 2009, and Japanese Patent Application No. 2010-054609, filed Mar. 11, 2010. The contents of the priority applications are hereby incorporated by reference in their entireties. 
     TECHNICAL FIELD 
     The present disclosure relates to a spare-tire installation structure for a vehicle that provides superior impact absorption properties upon collision with minimal addition to vehicle body weight. 
     BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The present disclosure relates to a spare-tire installation structure for a vehicle that provides superior impact absorption properties upon collision with minimal addition to vehicle body weight. 
     2. Description of the Related Art 
     A spare tire is structurally designed to have at least a predetermined strength to serve as a road tire by taking into account the force applied from a road surface inward or outward in the radial direction of the tire and the environment in which the spare tire may be used. 
     A typical spare tire, as assembled, has a rubber spare tire body fitted around a metal spare tire wheel. 
     The spare tire wheel integrally includes a substantially cylindrical drum equipped with the spare tire body and a substantially disk-shaped spoke surface located on the side of the drum that faces the outside of the vehicle when the spare tire is attached to the vehicle for use. 
     To install the spare tire in a trunk room provided in the rear of the vehicle, for example, the spare tire is accommodated in a spare-tire installation area provided on a floor panel surface in the rear of the vehicle so that the spoke surface lies in a substantially horizontal position. 
     However, if the spare tire is installed in a substantially horizontal orientation on the floor panel surface in the rear of the vehicle, the radial direction of the tire, in which the tire has relatively high rigidity, corresponds to the longitudinal direction of the vehicle that may also be the direction in which a crushable zone extends. 
     Because the spare tire and wheel are resistant to fracture or collapse, the spare tire may make it difficult to provide a desired crushable zone for the rear structure of the vehicle. This may degrade impact absorption properties in the event of a rear collision. 
     Accordingly, examples of known structures include one that allows the spare tire to be rotated so as to tilt frontward or rearward as the rear of the vehicle is deformed upon rear collision (see, for example, Japanese Unexamined Patent Application Publication No. 2006-137329) and one that allows the spare tire to fall toward the bottom of the vehicle without being held between other vehicle components to ensure a desired crushable zone (see, for example, Japanese Unexamined Patent Application Publication No. 2006-290272). 
     However, the structure that allows a conventional spare tire to be rotated so as to tilt frontward or rearward, and the structure that allows a conventional spare tire to fall toward the bottom of the vehicle without being held between other vehicle components to ensure a desired crushable zone result in a complicated vehicle structure and may, therefore, increase weight and production costs. 
     SUMMARY OF INVENTION 
     In one aspect, embodiments disclosed herein include a spare tire installation structure for a vehicle having a first rigid member disposed within a trunk compartment of the vehicle and a second rigid member configured vehicle rearward of the first rigid member and disposed within the trunk compartment of the vehicle, wherein the first rigid member and the second rigid member define a space to house a spare tire, and the second rigid member is configured to displace the spare tire vehicle forward and into the first rigid member in response to a rear collision to the vehicle. 
     In another aspect, embodiments disclosed herein include a method to split a spare tire of a vehicle including disposing a first rigid member in a trunk compartment of the vehicle, disposing a second rigid member in the trunk compartment and vehicle rearward of the first rigid member, disposing a spare tire between the first rigid member and the second rigid member, and configuring the second rigid member to displace the spare tire vehicle forward and into the first rigid member in response to a rear-end collision to the vehicle. 
     In another aspect, embodiments disclosed herein include a spare tire installation structure of a vehicle including a means for displacing a spare tire disposed in a trunk compartment of a vehicle and a means for splitting a wheel of the spare tire disposed in the trunk compartment and vehicle forward of the means for displacing the spare tire, wherein the means for displacing the spare tire is configured to displace the spare tire in a vehicle forward direction into the means for splitting a wheel in response to a rear-end collision to the vehicle. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a spare-tire installation structure according to one or more embodiments of the present disclosure as viewed from the rear of a vehicle, illustrating the overall structure, with an enlarged perspective view, partially in cross section, of a relevant part of the spare-tire installation structure; 
         FIG. 2  is a schematic plan view of the spare-tire installation structure according to one or more embodiments of the present disclosure, illustrating a spare-tire installation area in the rear of the vehicle and the vicinity thereof; 
         FIG. 3  is a schematic side view of the spare-tire installation structure according to the embodiment, illustrating the rear structure of the vehicle; 
         FIG. 4  is a schematic side view of the spare-tire installation structure according to one or more embodiments of the present disclosure, illustrating the rear structure of the vehicle before rear collision; 
         FIG. 5  is a schematic side view of the spare-tire installation structure according to one or more embodiments of the present disclosure, illustrating the rear structure of the vehicle after rear collision; 
         FIG. 6(   a ) is a schematic perspective view of a component of a spare-tire installation structure in accordance with one or more embodiments of the present disclosure;  FIG. 6(   b ) is a cross-sectional view taken along line A-A in  FIG. 6(   a ); 
         FIG. 7(   a ) is a schematic perspective view of a component of a spare-tire installation structure in accordance with one or more embodiments of the present disclosure;  FIG. 7(   b ) is a cross-sectional view taken along line B-B in  FIG. 7(   a ); 
         FIG. 8  is a schematic side view of a component of a spare-tire installation structure in accordance with one or more embodiments of the present disclosure; 
         FIG. 9  is a schematic enlarged side view of the spare-tire installation structure in accordance with one or more embodiments of the present disclosure, showing an example of the state of a spare tire after collision; 
         FIG. 10  is an enlarged perspective view, partially in cross section, of a component of a spare-tire installation structure in accordance with one or more embodiments of the present disclosure; 
         FIG. 11  is an enlarged cross-sectional view of a component of a spare-tire installation structure in accordance with one or more embodiments of the present disclosure; 
         FIG. 12  is a schematic enlarged cross-sectional view of the spare-tire installation structure in accordance with one or more embodiments of the present disclosure, showing an example of the state of a spare tire after collision; 
         FIG. 13  is a schematic cross-sectional view, taken along a line corresponding to line C-C in  FIG. 10 , of a component of a spare-tire installation structure in accordance with one or more embodiments of the present disclosure; 
         FIG. 14  is an enlarged perspective view of a component of a spare-tire installation structure in accordance with one or more embodiments of the present disclosure; 
         FIG. 15  is a schematic enlarged cross-sectional view, taken along line D-D in  FIG. 14 , of a spare-tire installation structure in accordance with one or more embodiments of the present disclosure, showing an example of the state of a spare tire after collision; 
         FIG. 16  is a schematic side view of a spare-tire installation structure of Example 7 of the embodiment, illustrating the rear structure of the vehicle before collision; 
         FIG. 17  is a schematic side view of the spare-tire installation structure in accordance with one or more embodiments of the present disclosure, illustrating the rear structure of the vehicle after collision; 
         FIG. 18  is a schematic side view, partially in cross-section, of a spare-tire installation structure in accordance with one or more embodiments of the present disclosure; 
         FIG. 19  is a schematic side view, partially in cross-section, of a spare-tire installation structure of Example 9 of the embodiment, illustrating the rear structure of the vehicle; 
         FIG. 20  is a schematic perspective view, partially in cross-section, of a spare-tire installation structure in accordance with one or more embodiments of the present disclosure; 
         FIG. 21  is a schematic side view, partially in cross-section, of a spare-tire installation structure in accordance with one or more embodiments of the present disclosure; and 
         FIG. 22  is a schematic perspective view, partially in cross-section, of a spare-tire installation structure in accordance with one or more embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     A spare-tire installation structure according to one or more embodiments of the present disclosure will now be described with reference to the drawings. 
       FIGS. 1 to 5  show a spare-tire installation structure according to one or more embodiments of the present disclosure. 
     First, the overall structure will be described. For the spare-tire installation structure according to one or more embodiments of the present disclosure, a trunk room  3  may be provided in a rear section  2  of a vehicle  1 . 
     A pair of rear side members  5  may be disposed to the left and right of a floor  4  of the trunk room  3  in the width direction of the vehicle  1 . A rear cross member  6 , serving as a first rigid member, may extend from one rear side member  5  to another rear side member  5 . A rear bumper reinforcement  7 , serving as a second rigid member, may extend so that a longitudinal direction may lie along rear ends of the rear side members  5 . 
     A rear floor panel  8  may be disposed between the rear bumper reinforcement  7  and the rear cross member  6  and may have a spare-tire installation area  9  where a spare tire  10  may be installed in a substantially horizontal position. 
     As shown, the spare tire  10  may include a metal spare tire wheel  11  and a rubber spare tire body  12 . Further, the spare tire wheel  11  may include a wide cylindrical drum  16  around which the spare tire body  12  may be fitted and secured, and a spoke surface  15  on one side of the drum  16 . When the spare tire  10  is installed in the vehicle  1 , the spoke surface  15  may face outward in the lateral direction of the vehicle  1 , and the drum  16  may be positioned inward in the lateral direction of the vehicle  1  from the spoke surface  15 . 
     The spare tire wheel  11  may be fixed to the rear floor panel  8  using, for example, bolts, nuts, and/or any other attachment means (not shown) when the spare tire  10  is installed in a substantially horizontal position in the spare-tire installation area  9  defined in the rear section  2  of the vehicle  1 . 
     The drum  16 , located inside the spare tire body  12 , may have the spare tire body  12  fitted therearound. The drum  16  may include an annular inner drum portion  17  disposed on the side of the drum  16  opposite the spoke surface  15  and an outer drum portion  18  disposed on the same side of the spoke surface  15  such that the drum portion  18  surrounds the spoke surface  15 . The inner and outer drum portions  17  and  18  may join at a junction  19 . 
     An annular outer rim ring  18   a  may be integrally formed at the distal end (outermost when installed on the vehicle  1 ) of the outer drum portion  18  to prevent the spare tire body  12  fitted therearound from coming off. In addition, an annular inner rim ring  17   a  may be integrally formed at the distal end (innermost end when installed on the vehicle  1 ) of the inner drum portion  17  to prevent the spare tire body  12  fitted therearound from coming off. 
     As shown in  FIG. 1 , the rim width w 1 , between the inner and outer rim rings  17   a  and  18   a , may be substantially equal to, or slightly smaller than, the height h 1  of the circumferential surface of the tire body  12 . 
     The rear bumper reinforcement  7  may be disposed at the rear of the spare tire  10  and may be formed so that the height hb of a front surface  7   a  of the rear bumper reinforcement  7  is larger than the rim width w 1  of the drum  16  of the spare tire wheel  11 , such that an upper surface of the rear bumper reinforcement  7  may extend above the drum  16  (above outer rim  18   a  in  FIG. 3 ) and a lower surface of the rear bumper reinforcement  7  may extend below the drum  16  (below outer rim ring  17   a  in  FIG. 3 ). 
     In accordance with one or more embodiments of the present disclosure, the junction  19  of the drum  16 , where the inner and outer drum portions  17  and  18  may join, may be defined as a rigidity-varying portion of the spare tire wheel  11 . The junction  19  may be formed in a different shape from the other drum portions  17  and  18  in terms of thickness and bending angle so that the rigidity may vary in the direction along the central axis of rotation  14 . 
     In accordance with one or more embodiments of the present disclosure, as shown in  FIG. 3 , the drum  16  may have a spoke-surface-fixed portion  16   a  near the junction  19  of the spare tire wheel  11 . A peripheral edge  15   a  of the spoke surface  15  may be internally adjacent to the spoke-surface-fixed portion  16   a  and may be integrally fixed over the entire circumference thereof. 
     In addition, a wheel-fracture facilitating member  20  may be provided on the vehicle side as part of the first rigid member so as to extend from the rear surface  6   a  of the rear cross member  6  toward the spare-tire installation area  9 . The wheel-fracture facilitating member  20  may be disposed adjacent to the inner drum portion  17  side with respect to the junction  19 . In accordance with one or more embodiments of the present disclosure, the wheel-fracture facilitating member  20  may be a wedge and may have the shape of an acute isosceles triangle with an acute end  20   a  in plan view. The acute end  20   a  may abut the circumferential surface of the spare tire  10  on the side thereof facing the front of the vehicle  1 . 
     During a rear collision, the acute end  20   a  may cut a wedge form into the front of the circumferential surface of the spare tire body  12  fitted around the spare tire wheel  11  on the inner drum portion  17  side thereof, thus easily coming into abutment with the annular inner drum portion  17 . 
     As shown in  FIG. 4 , the front surface  7   a  of the rear bumper reinforcement  7  may come into abutment with the circumferential surface of the spare tire body  12  on the side  12   a  thereof facing the rear of the vehicle  1 . The rear bumper reinforcement  7  may contact the spare tire  10  over a region along the height h 1  during a rear collision, thus pushing the spare tire  10  toward the front of the vehicle  1 , as shown in  FIG. 5 . 
     As shown in  FIGS. 1 to 3 , the spare tire  10  may be installed in the spare-tire installation area  9  of the trunk room  3  of the vehicle  1 . Further, as shown in  FIGS. 4 and 5 , if another vehicle  21  collides with the rear end of the vehicle  1 , the rear bumper and the rear bumper reinforcement  7  may be deformed as the rear section  2  of the vehicle  1  is deformed. 
     The front surface  7   a  of the rear bumper reinforcement  7  may be disposed opposite the spare tire  10  over the rim width w 1  between the inner and outer rim rings  17   a  and  18   a  of the drum  16  of the spare tire wheel  11 . Upon impact, the front surface  7   a  may come into abutment with the circumferential surface of the spare tire body  12  on the side  12   a  thereof facing the rear of the vehicle  1  over a region along the height h 1 . 
     As shown in  FIG. 5 , during a rear collision, the spare tire  10  may be pressed toward the front of the vehicle  1  in a vertical direction of the vehicle  1 , may be reliably moved toward the front of the vehicle  1  without rotating, and may be pushed toward the rear cross member  6  disposed adjacent to the inner drum portion  17 . 
     As a front end  12   b  of the circumferential surface of the spare tire body  12  of the spare tire  10  may be moved into abutment with the acute end  20   a  of the wheel-fracture facilitating member  20  provided on the rear surface  6   a  of the rear cross member  6 , the spare tire  10  may be held between the front surface  7   a  of the rear bumper reinforcement  7  and the rear surface  6   a  of the rear cross member  6  and may be pressed therebetween in a longitudinal direction of the vehicle  1 . 
     During a rear collision, the acute end  20   a  of the wheel-fracture facilitating member  20  may cut into the front end  12   b  of the circumferential surface of the spare tire body  12  on the inner drum portion  17  side thereof, thus reaching the inner rim ring  17   a  of the annular inner drum portion  17 . 
     The acute end  20   a  may then cut into the annular inner rim ring  17   a  integrally formed at the innermost end of the inner drum portion  17  of the drum  16  to fracture the inner drum portion  17  into left and right halves in a lateral direction of the vehicle  1 . 
     At the same time, a shear force acting in the longitudinal direction of the vehicle  1  may be applied between the inner drum portion  17 , located opposite the wheel-fracture facilitating member  20 , and the outer drum portion  18 , which may then be moved upward and forward toward the front of the vehicle  1  upon rear collision, with respect to the inner drum portion  18 . 
     In accordance with one or more embodiments of the present disclosure, the height of the junction  19  may correspond to the height h 3  of a top corner between the rear surface  6   a  and a top surface  6   b  of the rear cross member  6 . Thus, the spare tire wheel  11  may easily fracture at the junction  19 , where the rigidity of the drum  16  may vary significantly. 
     As indicated by the two-dot chain line in  FIG. 5 , the outer drum portion  18  and the spoke surface  15 , which may have a relatively high rigidity and may be located on the top side of the spare tire  10 , may be moved toward the front of the vehicle  1  without hindrance while being separated diagonally upward from the inner drum portion  17 . 
     Thus, a desired crushable zone is ensured so that the vehicle body can be crushed without hindrance. With the desired crushable zone, the body structure provides superior impact absorption properties. 
     The wheel-fracture facilitating member  20 , having the shape of the acute isosceles triangle with the acute end  20   a  in plan view, may fracture the inner drum portion  17  into left and right halves in the width direction of the vehicle  1 , each half being bendable and/or compressible. The left and right halves of the inner drum portion  17  may have a lower rigidity than the annular spare tire wheel  11  as a whole. 
     Thus, there may be no hindrance to facilitation of deformation upon rear collision in the rear section  2  of the vehicle  1 , so that the vehicle body may be crushed without hindrance. This may allow a crushable zone to provide superior impact absorption properties. 
     In addition, the wheel-fracture facilitating member  20  may be simply fixed to a conventional rear cross member  6  on one side of the inner drum portion  17  so as to protrude from the rear surface  6   a  of the rear cross member  6 . This may be achieved with the minimum increase in a number of components. 
     Thus, the wheel-fracture facilitating member  20  may be easy to locate and fix, and the impact absorption properties upon rear collision may be improved by a simple, lightweight structure. 
     In the spare-tire installation structure according to one or more embodiments of the present disclosure, the junction  19  (the rigidity-varying portion of the spare tire wheel  11 ) may be defined near the spoke-surface-fixed portion  16   a  of the drum  16  to which the peripheral edge  15   a  of the spoke surface  15  may be fixed. 
     Because the spoke surface  15  may have a higher rigidity than the drum  16 , the rigidity of the spare tire wheel  11  may vary significantly near the spoke-surface-fixed portion  16   a  to which the peripheral edge  15   a  may be fixed. 
     In the spare-tire installation structure according to one or more embodiments of the present disclosure, additionally, the junction  19  between the inner and outer drum portions  17  and  18  of the drum  16  may defined as the rigidity-varying portion of the spare tire wheel  11 . Thus, the position of the rigidity-varying portion may be easily changed in the vertical direction of the vehicle  1 . 
     In the spare-tire installation structure according to one or more embodiments of the present disclosure, additionally, the spoke-surface-fixed portion  16   a  of the drum  16  to which the peripheral edge  15   a  of the spoke surface  15  may be fixed may be defined at the junction  19  between the inner and outer drum portions  17  and  18 . Thus, the rigidity of the spare tire wheel  11  may vary significantly at the junction  19 . 
       FIGS. 6(   a ) and  6 ( b ) show a spare-tire installation structure in accordance with one or more embodiments of the present disclosure. The same or equivalent elements as in the embodiments described above are denoted by the same reference numerals. 
     In the spare-tire installation structure as shown in  FIG. 6(   a ), instead of the wheel-fracture facilitating member  20  of the embodiment described above, a wedge-shaped wheel-fracture facilitating member  22  serving as part of the first rigid member may be fixed to the rear surface  6   a  of the rear cross member  6  serving as the first rigid member and may have an end  22   a  protruding toward the spare-tire installation area  9 , that is, toward the rear of the vehicle  1 . 
     As shown in  FIG. 6(   b ), the wedge-shaped wheel-fracture facilitating member  22  may have the shape of a substantially right triangle in side view and may be disposed adjacent to the inner drum portion  17  of the drum  16  such that the height of the end  22   a  in the vertical direction of the vehicle  1  may be close to that of the junction  19  of the spare tire wheel  11  of the spare tire  10 . 
     In accordance with one or more embodiments of the present disclosure, the wedge-shaped wheel-fracture facilitating member  22  may have the shape of a substantially right triangle in side view, and the height h 2  of the end  22   a  in the vertical direction of the vehicle  1  may be close to that of the junction  19  of the spare tire wheel  11  of the spare tire  10 . 
     Thus, as the spare tire  10  is moved toward the front of the vehicle  1  upon rear collision, the end  22   a  of the wedge-shaped wheel-fracture facilitating member  22  may come into abutment with and cut into the front end  12   b  of the circumferential surface of the spare tire body  12  of the spare tire  10  while imposing a load on the drum portion  17  that may bend. 
     Forming a cut with a longitudinal direction lying in a substantially horizontal direction near the junction  19 , the end  22   a  may facilitate a fracture between the inner and outer drum portions  17  and  18 . 
     Referring now to  FIG. 7 , a spare-tire installation structure in accordance with one or more embodiments of the present disclosure is shown. The same or equivalent elements as in the embodiments described above are denoted by the same reference numerals. 
     In the spare-tire installation structure as shown in  FIG. 7 , instead of the wheel-fracture facilitating member  20  of the embodiments described above, a rectangular wheel-fracture facilitating member  23  may serve as part of the first rigid member that may be fixed to the rear surface  6   a  of the rear cross member  6  serving as the first rigid member. 
     The rectangular wheel-fracture facilitating member  23  may have a substantially rectangular contact end surface  23   a  located on a rear end thereof so as to protrude toward the spare-tire installation area  9 , that is, toward the rear of the vehicle  1 . The contact end surface  23   a  may be located adjacent to the inner drum portion  17  of the spare tire wheel  11 . 
     As shown in  FIG. 7 , the rectangular wheel-fracture facilitating member  23  may come into abutment with the front end  12   b  of the circumferential surface of the spare tire body  12  over a wide area on the inner drum portion  17  side thereof so that the contact end surface  23   a  may come into surface contact with the spare tire  10 . 
     Thus, the possibility of the spare tire  10  deviating from the desired movement direction upon rear collision may be reduced. Accordingly, the spare tire  10  may be stably fractured. 
     Referring now to  FIGS. 8 and 9 , a spare-tire installation structure in accordance with one or more embodiments of the present disclosure is shown. The same or equivalent elements as in the embodiments described above are denoted by the same reference numerals. 
     In the spare-tire installation structure as shown in  FIGS. 8 and 9 , instead of the wheel-fracture facilitating member  20  of the embodiment described above, the rear cross member  6 , which constitutes part of the rear section  2  of the vehicle  1 , may serve as the first rigid member. 
     Specifically, as shown in  FIGS. 8 and 9 , the rear cross member  6  may be disposed opposite the front end  12   b  of the circumferential surface of the spare tire  10  on the inner drum portion  17  side with respect to the junction  19 . 
     As indicated by the solid line in  FIG. 9 , the width direction the cross-sectional shape of the rear cross member  6  lies in the vertical direction of the vehicle  1 . The position of the top surface  6   b  of the rear cross member  6  in the vertical direction of the vehicle  1  corresponds with a position of the junction  19  in the vertical direction of the vehicle  1 . 
     As shown in  FIGS. 8 and 9 , if the spare tire  10  is pushed toward the front of the vehicle  1  upon a rear collision the front end  12   b  of the circumferential surface of the spare tire body  12  may come into abutment with the rear surface  6   a  of the rear cross member  6  on the inner drum portion  17  side thereof. 
     Thus, the drum  16  of the spare tire wheel  11  may be pressed on the inner drum portion  17  side, where the inner rim ring  17   a  may be disposed, through the front end  12   b  of the circumferential surface of the spare tire body  12  so that a holding force may act on the drum  16  with respect to the junction  19 . 
     Accordingly, the holding pressure applied in the longitudinal direction of the vehicle  1  may act as a shear force to separate the outer drum portion  18  and the spoke surface  15  from the inner drum portion  17 , as indicated by the two-dot chain lines shown in  FIG. 9 . 
     As shown in  FIG. 8 , the height of the junction  19  may correspond with the height h 4  of the top corner where the top end of the rear surface  6   a  and the top surface  6   b  of the rear cross member  6  join. The spare tire wheel  11  may, therefore, be easily fractured at the junction  19 , where the rigidity of the drum  16  may vary significantly. 
     Thus, there may be no hindrance to facilitation of deformation upon rear collision in the rear section  2  of the vehicle  1 . This may allow the desired crushable zone to provide superior impact absorption properties. 
     In addition, the rear cross member  6  may be simply disposed on the inner drum portion  17  side with respect to the junction  19 , which may serve as the rigidity-varying portion of the spare tire wheel  11 . This may allow the impact absorption properties upon rear collision to be improved by a simple, lightweight structure. 
     In the spare-tire installation structure as shown in  FIGS. 8 and 9 , the rear cross member  6 , which constitutes part of the rear section  2  of the vehicle  1 , may serve as the first rigid member. This may reduce the number of components, thus alleviating an increase in body weight and cost. 
     Referring now to  FIGS. 10-12 , a spare-tire installation structure in accordance with one or more embodiments of the present disclosure is shown. The same or equivalent elements as in the embodiments described above are denoted by the same reference numerals. 
     In the spare-tire installation structure as shown in  FIGS. 10-12 , the spare tire  10  may be installed such that the positions of the inner and outer drum portions  17  and  18  in the vertical direction are opposite to those shown in  FIGS. 8 and 9 . 
     In addition, the rear cross member  6 , which may be provided instead of the wheel-fracture facilitating member  20  of the embodiments described above, may be disposed opposite the front end  12   b  of the circumferential surface of the spare tire  10  on the inner drum portion  17  side with respect to the junction  19 , which may serve as the rigidity-varying portion of the spare tire wheel  11 . 
     As shown in  FIG. 11 , the rear cross member  6  may have a shape with a width lying in the longitudinal direction of the vehicle  1 . The rear surface  6   a  of the rear cross member  6  may be located on the inner drum portion  17  side such that the position of the bottom surface  6   c  of the rear cross member  6  in the vertical direction of the vehicle  1  may correspond with the position of the junction  19  in the vertical direction of the vehicle  1 . 
     As shown in  FIGS. 10-12 , if the spare tire  10  is pushed toward the front of the vehicle  1  upon rear collision, the front end  12   b  of the circumferential surface of the spare tire  10  may come into abutment with the rear surface  6   a  of the rear cross member  6  on the inner drum portion  17  side thereof Thus, a shearing force may act on the drum  16  of the spare tire wheel  11  with respect to the junction  19  in the longitudinal direction of the vehicle  1  to separate the outer drum portion  18  and the spoke surface  15  from the inner drum portion  17 , as shown in  FIG. 12 . 
     Accordingly, there is no hindrance to facilitation of deformation upon rear collision in the rear section  2  of the vehicle  1 . This may allow for the desired crushable zone to provide superior impact absorption properties. 
     In addition, the rear cross member  6  may be simply disposed on the inner drum portion  17  side with respect to the junction  19 , which may serve as the rigidity-varying portion of the spare tire wheel  11 . This may eliminate the need for another component and allows the impact absorption properties upon rear collision to be improved by a simple, lightweight structure. 
     Now referring to  FIG. 13 , a spare-tire installation structure in accordance with one or more embodiments of the present disclosure is shown. The same or equivalent elements as described above are denoted by the same reference numerals. 
     As shown in  FIG. 13 , the rear cross member  6  may be disposed in front of the spare-tire installation area  9  such that the width of the rear cross member  6  lies in the vertical direction of the vehicle  1 . In addition, the position of the bottom surface  6   c  of the rear cross member  6  in the vertical direction of the vehicle  1  may correspond with the position of the junction  19  in the vertical direction of the vehicle  1 . 
     In the spare-tire installation structure as shown in  FIG. 13 , the width of the rear cross member  6  may lie in the vertical direction of the vehicle  1 . Thus, the rear surface  6   a  may provide a sufficient area for receiving pressure from the spare tire  10  while alleviating an increase in weight due to an increase in the cross-sectional area of the rear cross member  6 . 
     Now referring to  FIGS. 14 and 15 , a spare-tire installation structure in accordance with one or more embodiments of the present disclosure is shown. The same or equivalent elements as described above are denoted by the same reference numerals. 
     As shown in  FIGS. 14 and 15 , a rear cross member  26  may serve as the first rigid member and may extend in the lateral direction of the vehicle  1 . The rear cross member  26  may be formed so as to have a substantially rectangular cross-sectional shape with a width lying in the longitudinal direction of the vehicle  1 . 
     A rear surface  26   a  of the rear cross member  26  may be located adjacent to the spare tire  10 , and the position of a top surface  26   b  of the rear cross member  26  in the vertical direction of the vehicle  1  may correspond with a position of the junction  19  in the vertical direction of the vehicle  1 . 
     As shown in  FIG. 14 , the rim width w 1  between the inner and outer rim rings  17   a  and  18   a  may be substantially equal to, or slightly smaller than, a height h 1  of the tire body (not shown) in a substantially horizontal orientation on the side thereof facing the rear of the vehicle  1 . 
     The rear bumper reinforcement  7 , may be disposed opposite the rear of the spare tire  10 , may be formed so that a height he of the front surface  7   a  of the rear bumper reinforcement  7  may be larger than a rim width w 1  of the drum  16  of the spare tire wheel  11  and may exceed both rim ends thereof, that is, the inner and outer rim ring  17   a  and  18   a , in the direction along the central axis of rotation  14 , namely, the axle direction of the drum  16 . 
     When the spare tire  10 , including the spare tire body  12 , is installed in a substantially horizontal orientation, the rear bumper reinforcement  7  may be located opposite the circumferential surface of the spare tire body  12  on the side  12   a  thereof facing the rear of the vehicle  1  along the vertical direction of the vehicle  1 . 
     The front surface  7   a  of the rear bumper reinforcement  7  may come into abutment with the circumferential surface of the spare tire body  12  on the side  12   a  thereof facing the rear of the vehicle  1  along a height larger than the rim width w 1  between the inner and outer rim rings  17   a  and  18   a  in the vertical direction. 
     As shown in  FIG. 15 , if the spare tire  10  is pushed toward the front of the vehicle  1  by the front surface  7   a  of the rear bumper reinforcement  7  as a result of deformation upon rear collision, the front end  12   b  of the circumferential surface of the spare tire  10  may come into abutment with the rear surface  26   a  of the rear cross member  26  on the inner drum portion  17  side. 
     The front surface  7   a  of the rear bumper reinforcement  7  may come into abutment with the circumferential surface of the spare tire body  12  (not shown) on the side  12   a  thereof facing the rear of the vehicle  1  along a height larger than the rim width w 1  in the vertical direction of the vehicle  1 , thus reliably pressing the spare tire  10  toward the front of the vehicle  1 . 
     Thus, as indicated by the two-dot chain lines in  FIG. 15 , the spare tire  10  may be reliably moved toward the front of the vehicle  1  without rotating with the spare tire body  12  between the front surface  7   a  of the rear bumper reinforcement  7  and the rear ends of the inner and outer rim rings  17   a  and  18   a . The spare tire  10  may be pressed between the front surface  7   a  of the rear bumper reinforcement  7  and the rear surface  26   a  of the rear cross member  26  disposed adjacent to the inner drum portion  17 . A shear force may then act on the inner drum portion  17  of the drum  16  of the spare tire wheel  11  with respect to the junction  19  in the longitudinal direction of the vehicle  1 . 
     As indicated by the two-dot chain lines in  FIG. 15 , the outer drum portion  18  and the spoke surface  15  may be separated diagonally upward from the inner drum portion  17  toward the front of the vehicle  1 . 
     As shown in  FIG. 15 , the spare tire  10  may be pushed toward the front of the vehicle  1  and the front surface  7   a  of the rear bumper reinforcement  7  may come into abutment with the circumferential surface of the spare tire body  12  (not shown) on the side  12   a  thereof facing the rear of the vehicle  1  along the vertical direction of the vehicle  1 . 
     Thus, the inner and outer rim rings  17   a  and  18   a  may be simultaneously pressed toward the front of the vehicle  1  so that the spare tire  10  may be stably and reliably moved toward the front of the vehicle  1 . 
     In addition, when the front end  12   b  of the circumferential surface of the spare tire  10  may come into abutment with the rear surface  26   a  of the rear cross member  26  on the inner drum portion  17  side, the rear cross member  26  may ensure sufficient rigidity to receive a force applied in the longitudinal direction of the vehicle  1  without an increase in weight because the rear cross member  26  may have a width in the longitudinal direction of the vehicle  1 . 
     Referring now to  FIGS. 16 and 17 , a spare-tire installation structure in accordance with one or more embodiments of the present disclosure is shown. The same or equivalent elements as described above are denoted by the same reference numerals. 
     As shown in  FIGS. 16 and 17 , a rear suspension member  46  that may serve as the first rigid member may be provided instead of the rear cross member  6  of the spare-tire installation structure as shown in  FIG. 11  and in embodiments disclosed herein. The rear suspension member  46  may be provided on the forward side of the spare-tire installation area  9  with a longitudinal direction lying in the width direction of the vehicle  1 . 
     The position of a bottom surface  46   b  of the rear suspension member  46  in the vertical direction of the vehicle  1  may correspond with the position of the junction  19  in the vertical direction of the vehicle  1 . Thus, a rear surface  46   a  of the rear suspension member  46  may be located adjacent to the front end  12   b  of the circumferential surface of the spare tire body  12  of the spare tire  10  at the inner drum portion  17  side thereof The inner drum portion  17  may be disposed upward with respect to the junction  19  of the drum  16  of the spare tire wheel  11 , that is, on the side facing away from the outer drum portion  18  with the spoke surface  15  facing downward. 
     In the spare-tire installation structure in accordance with one or more embodiments of the present disclosure and as shown in  FIGS. 16 and 17 , if another vehicle  21  collides with the rear section  2  of the vehicle  1 , the front surface  7   a  of the rear bumper reinforcement  7  may press the spare tire  10  toward the forward side of the spare-tire installation area  9  in the vertical direction of the vehicle  1 . 
     Thus, the spare tire  10  may be pushed and reliably moved toward the front of the vehicle  1  without rotating so that the front end  12   b  of the circumferential surface of the spare tire body  12  may come into abutment with the rear surface  46   a  of the rear suspension member  46  disposed on the side facing away from the spoke surface  15 . Accordingly, the spare tire  10  may be held between the front surface  7   a  of the rear bumper reinforcement  7  and the rear surface  46   a  of the rear suspension member  46  and may be pressed therebetween in the longitudinal direction of the vehicle  1  so that a shear force may act around the junction  19  through the spare tire body  12 . 
     As a result, the inner drum portion  17 , located on the top side of the spare tire wheel  11 , may be compressed in the longitudinal direction of the vehicle  1 , whereas the outer drum portion  18  and the spoke surface  15  may be separated from the inner drum portion  17  toward the bottom of the vehicle  1 . Thus, the existing rear suspension member  46  may be used as the first rigid member instead of providing another component such as the wheel-fracture facilitating member  20  as in embodiments described above. 
     At the same time, because the rear cross member  6  does not have to be used as the rigid member as in the embodiments described above, the flexibility of the layout, including the shape of the vehicle body and the position of the spare-tire installation area  9 , may be increased. In addition, the structure may be simplified so that the possibility of increased weight may be reduced. 
     Referring now to  FIG. 18 , a spare-tire installation structure in accordance with one or more embodiments of the present disclosure is shown. The same or equivalent elements as in the embodiments described above are denoted by the same reference numerals. 
     In the spare-tire installation structure as shown in  FIG. 18 , a cross member  103  may be provided between a cabin  33  and the trunk room  3  with its longitudinal direction lying in the lateral direction of the vehicle  1 . The cross member  103  may protrude to a predetermined height h 9  above the rear side members  5  so as to prevent a fractured and/or separated component of the spare tire  10  from intruding into the cabin  33 . 
     In the spare-tire installation structure as shown in  FIG. 18 , the cross member  103  may be provided on the side of the rear cross member  6  facing the front of the vehicle  1  so as to protrude to the predetermined height h 9  above the rear side members  5 . Thus, the cross member  103  may block a fractured and/or separated component of the spare tire  10  from moving toward the front of the vehicle  1  upon rear collision and may prevent the fractured and/or separated component from intruding into the cabin  33 . 
     Now referring to  FIGS. 19 and 20 , a spare-tire installation structure in accordance with one or more embodiments of the present disclosure is shown. The same or equivalent elements as in the embodiments described above are denoted by the same reference numerals. 
     In the spare-tire installation structure as shown in  FIGS. 19 and 20 , a guide stopper  104  may be attached to a front end  9   a  of the spare-tire installation area  9  on the floor  4  of the trunk room  3  formed in the rear section  2  of the vehicle  1  so as to cover part of a front top surface of the spare-tire installation area  9 . The guide stopper  104  may include an attachment portion  104   a  attached to the front end  9   a  of the spare-tire installation area  9  and an energy-absorbing portion  104   b  extending from the attachment portion  104   a  toward the rear of the vehicle  1  so as to be substantially crank-shaped in side view, as indicated by the solid line in  FIG. 19 , and may be bendable toward the top of the vehicle  1 , as indicated by the two-dot chain line. 
     In the spare-tire installation structure as shown in  FIGS. 19 and 20 , even if the spare tire body  12  of the spare tire  10 , or the outer drum portion  18  and the spoke surface  15 , is moved upward toward the front of the vehicle  1  upon rear collision, as indicated by the two-dot chain line in  FIG. 19 , the energy-absorbing portion  104   b  of the guide stopper  104  may be bent so as to absorb kinetic energy associated with the movement of the spare tire  10 , thereby blocking the movement toward the front of the vehicle  1 . 
     In accordance with one or more embodiments of the present disclosure, the entirety of the spare tire  10  may be moved or may not be moved; instead, the portion on the outer drum portion  18  side separated at the junction  19  bay be moved, with the inner drum portion  17  remaining in the spare-tire installation area  9 . Thus, the target value for the amount of energy absorbed by the guide stopper  104  may be set to be lower than that absorbed when the guide stopper  104  receives the movement of the entire spare tire  10 . Accordingly, a compact, lightweight guide stopper  104  may be used to alleviate an increase in the weight of the rear section  2  of the vehicle  1 . 
     Now referring to  FIGS. 21 and 22 , a spare-tire installation structure in accordance with one or more embodiments of the present disclosure is shown. The same or equivalent elements as in the embodiments described above are denoted by the same reference numerals. 
     In the spare-tire installation structure as shown in  FIGS. 21 and 22 , an upper floor panel  105  may be attached to the front end  9   a  of the spare-tire installation area  9  on the floor  4  of the trunk room  3  formed in the rear section  2  of the vehicle  1  so as to cover the front top surface of the spare-tire installation area  9  along the lateral direction of the vehicle  1 . The upper floor panel  105  may include an attachment surface portion  105   a  attached to the front end  9   a  of the spare-tire installation area  9  and an upper partitioning portion  105   b  extending from the attachment surface portion  105   a  toward the rear of the vehicle  1  in a substantially flat shape so as to cover the front of the space above the spare-tire installation area  9 , as indicated by the solid line in  FIG. 21 . A capturing space  106  having a predetermined height h 10  in the vertical direction of the vehicle  1  may be formed between the front end  9   a  of the floor  4  and the upper partitioning portion  105   b.    
     In the spare-tire installation structure as shown in  FIGS. 21 and 22 , even if the spare tire body  12  of the spare tire  10 , or the outer drum portion  18  and the spoke surface  15 , is moved from the spare-tire installation area  9  toward the front of the vehicle  1  upon rear collision, the capturing space  106  formed between the upper partitioning portion  105   b  of the upper floor panel  105  and the front end  9   a  of the floor  4  may receive the upper separated portion of the spare tire and prevent the separated portion from entering the passenger compartment of the vehicle. 
     In accordance with one or more embodiments of the present disclosure, the portion on the outer drum portion  18  side separated from the spare tire  10  at the junction  19  may be moved, with the inner drum portion  17  remaining in the spare-tire installation area  9 . Thus, the target value for the amount of energy absorbed by the upper floor panel  105  required for the capturing space  106  to capture the spare tire  10  may be set to be lower than that absorbed when the upper floor panel  105  receives the movement of the entire spare tire  10 . Accordingly, a compact, lightweight upper floor panel  105  may be used to alleviate an increase in the weight of the rear section  2  of the vehicle  1 . 
     Although the spare-tire installation structures discussed herein have been described with reference to the drawings, specific structures are not limited thereto; the invention encompasses design changes that do not depart from the spirit of the invention and should only be limited by the accompanying claims. 
     That is, whereas the spare tire  10  shown in the embodiment described above has the spare tire body  12  fitted around the drum  16  of the spare tire wheel  11 , the shape, number, and material of the spare tire are not particularly limited. It is possible to use a tire of any type or structure, such as a temporary tire, a run-flat tire, or a road tire, that may be accommodated in the spare-tire installation area  9  of the vehicle  1 . 
     In addition, although the spare tire  10  is described with a spoke surface  15  internally adjacent to the outer drum portion  18 , the type of spare tire is not so limited; the spoke surface may be internally adjacent to either of the drum portions that are, in use, located inside and outside in the axle direction, for example, to the inner drum portion  17 . 
     In addition, although the wheel-fracture facilitating member  20  may be disposed adjacent to the inner drum portion  17  with respect to the junction  19  in the embodiment described above, the wheel-fracture facilitating member  20  may be disposed adjacent to the outer drum portion  18 ; that is, the wheel-fracture facilitating member  20  may be disposed adjacent to at least one of the inner and outer drum portions  17  and  18 . 
     In addition, although the rigid member shown in the embodiment described above may be the wheel-fracture facilitating member  20 , which may have the acute end  20   a  abutting the spare tire  10 , and the rigid member shown in embodiments described herein is a wedge-shaped wheel-fracture facilitating member  22 , which may have the shape of a substantially right triangle in side view and is configured such that the height h 2  of the end  22   a  in the vertical direction of the vehicle  1  may be close to that of the junction  19  of the spare tire wheel  11  of the spare tire  10 , the shape of the rigid member is not so limited; the rigid member may have any shape, such as a wedge shape, a triangular shape, an oblate shape, and/or any other geometric shape that may prevent the spare tire  10  from deviating and that may stably fracture the spare tire  10 . 
     In addition, any portions of the first and second rigid members may come into abutment with the spare tire  10  in any manner. For example, the first and second rigid members may be constituted only by the rear cross member  6  and the rear bumper reinforcement  7 , respectively, or may be constituted by a pair of front and rear cross members. The shapes, numbers, positions, and materials of the first and second rigid members are not particularly limited as long as the first and second rigid members can fracture the spare tire  10  by imposing a local load on the spare tire wheel  11  while preventing it from deviating. 
     In addition, although in the embodiments described above the front surface  7   a  of the rear bumper reinforcement  7  may come into abutment with the circumferential surface of the spare tire body  12  on the side  12   a  thereof facing the rear of the vehicle  1  along the height h 1 , another component such as a rear suspension member, a muffler, or a trailer hitch may be used instead of the rear bumper reinforcement  7 . The shape, number, and material of the second rigid member are not particularly limited as long as the second rigid member can press the spare tire  10  in the spare-tire installation area  9  toward the first rigid member. 
     In addition, although described herein with the longitudinal direction of the cross-sectional shape of the rear cross member  6  lying in the vertical direction of the vehicle  1 , as indicated by the solid line in  FIG. 9 , the direction is not limited thereto; for example, the direction may lie in the longitudinal direction of the vehicle  1  so that the position of the top surface  6   b  of the rear cross member  6  in the vertical direction of the vehicle  1  may correspond with the position of the junction  19  in the vertical direction of the vehicle  1 , as indicated by the two-dot chain line in  FIG. 9 . The shape, number, and material of the rear cross member  6  are not particularly limited as long as the rear cross member  6  may be disposed adjacent to at least one of the inner drum portion  17 , on which the spoke surface  15  is not disposed, and the outer drum portion  18  with respect to the rigid-varying portion of the drum  16 , namely, the junction  19 . 
     While the disclosure has been presented with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the present disclosure. Accordingly, the scope of the invention should be limited only by the attached claims.