Abstract:
A body frame connection member connects a first side frame portion and a second side frame portion which constitute each side frame. The body frame connection member is provided with a mount surface, an opposite-side surface, and a reinforcing rib. The mount surface is configured such that a loading platform can be mounted thereon, and includes an outer-side edge. The opposite-side surface is facing the opposite side from the mount surface, and is a recessed surface recessed toward the mount surface. The reinforcing rib extends upward from the outer-side edge of the mount surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage application under 35 U.S.C. 371 and claims the benefit of PCT Application No. PCT/JP2012/074649 filed 26 Sep. 2012 which designated the United States, which PCT Application claimed the benefit of Japanese Patent Application No. 2011-220964 filed on Oct. 5, 2011, the disclosure of each of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a vehicle body frame connection member that forms a vehicle body frame, and more particularly, to a vehicle body frame connection member that forms a vehicle body frame for a truck on which a cargo bed is mounted, and a vehicle body frame structure including the vehicle body frame connection member. 
     BACKGROUND ART 
     In the prior art, a structure that increases convenience when entering and exiting a transit bus by eliminating steps from the entrance or exit has been proposed for a transit bus vehicle body frame. For example, patent document 1 describes a vehicle body frame including a side frame divided into a rear frame, which is located above the rear wheels, and a front frame, which is located in front of the rear wheels. The front frame is placed at a lower position than the rear frame. Then, a connection member connects the frames to each other. This eliminates the need for steps at the entrance or exit. 
     Recent trucks on which cargo beds are mounted also have lowered cargo beds so that more cargo can be carried within the specified size. A known side frame of a vehicle body frame for such a truck is an integrally casted frame curved near the axle to avoid the movable range of the axle. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-56445 
     SUMMARY OF THE INVENTION 
     In a side frame including a curved portion that projects toward the cargo bed as described above, the wheel well formed in the cargo bed needs to be large enough to accommodate the curved portion of the side frame in addition to the wheels. In the structure of the cargo bed, the size of the curved portion of the side frame enlarges the wheel wells toward the inner side of the cargo bed. As a result, although the lowered cargo bed increases the cargo capacity, in comparison to when the wheel wells accommodate only the wheels, the cargo capacity of the cargo bed is small. Thus, there is still room for improvement with regard to increasing the cargo capacity. 
     It is an object of the present invention to provide a vehicle body frame connection member and a vehicle body frame structure that allows for an increase in the cargo capacity of a lowered cargo bed. 
     To achieve the above object, one aspect of the present invention is a vehicle body frame connection member arranged on each of two side frames that are parallel to each other. The vehicle body frame connection member connects a first side frame portion and a second side frame portion of each side frame in a direction in which the side frame extends. The vehicle body frame connection member of each side frame includes an inner portion facing toward the other side frame and an outer portion facing away from the other side frame. The vehicle body frame connection member includes a setting surface formed so that a cargo bed is set thereon. The setting surface includes an outer edge corresponding to the outer portion. An opposite surface faces an opposite side of the setting surface. The opposite surface is a recessed surface recessed toward the setting surface. A reinforcement rib projects from the outer edge of the setting surface. 
     A further aspect of the present invention is a vehicle body frame structure including two side frames that are parallel to each other. Each side frame includes a first side frame portion and a second side frame portion. A vehicle body frame connection member connects the first side frame portion and the second side frame portion in a direction in which the side frame extends. The vehicle body frame connection member of each side frame includes an inner portion facing toward the other side frame and an outer portion facing away from the other side frame. The vehicle body frame connection member includes a setting surface formed so that a cargo bed is set thereon. The setting surface includes an outer edge corresponding to the outer portion. An opposite surface faces an opposite side of the setting surface. The opposite surface is a recessed surface recessed toward the setting surface. A reinforcement rib projects from the outer edge of the setting surface. 
     In one aspect of the present invention, the opposite surface facing the opposite side of the setting surface on which the cargo bed is set is a recessed surface that is recessed toward the setting surface. This allows for the arrangement of the vehicle body frame in which the opposite surface and the axle are faced toward each other. In such an arrangement, in a portion of the opposite surface recessed toward the setting surface, the axle, which faces toward the portion, is allowed to move toward the setting surface. Thus, the recessed surface of the opposite surface allows for movement of the axle to a position proximal to the setting surface. Consequently, the cargo bed, which is set on the setting surface, may be lowered. 
     In the vehicle body frame connection member, the opposite surface is recessed toward the setting surface. Thus, the formation of the recessed surface may lower the mechanical strength of the vehicle body frame connection member. In this respect, in one aspect of the present invention, the reinforcement rib projects from the outer edge of the setting surface. This increases the mechanical strength of the vehicle body frame connection member in comparison to when there is no reinforcement rib. In addition, the vehicle body frame connection member of each side frame includes the inner portion that faces toward the other side frame and the outer portion that faces away from the other side frame. The setting surface includes the outer edge that corresponds to the outer portion, and the reinforcement rib projects from the outer edge. This allows for substantially the entire setting surface to be used as a setting portion for the cargo bed. Further, the reinforcement rib may be used to position the cargo bed mounted on the vehicle body frame, and sideward displacement of the mounted cargo bed may be limited. 
     Preferably, in the outer edge of the setting surface, a height of the reinforcement rib from the setting surface is greatest at a location where the distance is smallest between the setting surface and the opposite surface. 
     The opposite surface is formed as a recessed surface, which is recessed toward the setting surface. Thus, in comparison to a structure in which the setting surface and the opposite surface are parallel to each other, the distance is decreased between the opposite surface and the setting surface. Further, in the outer edge of the setting surface where the reinforcement rib is arranged, the mechanical strength of the vehicle body frame connection member has a tendency of being lower at the portion where the distance is smallest between the setting surface and the opposite surface compared to other portions. 
     In this respect, in the above embodiment, the height of the reinforcement rib increases at the portion where the distance is smallest between the setting surface and the opposite surface. This allows for a limited increase in the height of the reinforcement rib from the setting surface when reinforcing mechanical strength. 
     Preferably, the opposite surface is an inwardly curved surface, and the height of the reinforcement rib from the setting surface increases as the distance decreases between the setting surface and the opposite surface. 
     In the above aspect, at locations along the outer edge of the setting surface, the height of the reinforcement rib from the setting surface increases as the distance decreases between the setting surface and the opposite surface. This allows for the height of the reinforcement rib from the setting surface to be suitable for reinforcing the mechanical strength with the reinforcement rib. 
     Preferably, the vehicle body frame connection member is a casting, and includes a first fastening portion, fastened to the first side frame portion by a fastening member, and a second fastening portion, fastened to the second side frame portion by a fastening member. 
     Generally, to allow for satisfactory welding to another member, there are many limitations to the components that may be contained in a casting. In the above aspect, the vehicle body frame connection member includes the first and second fastening portions, which are fastened by fastening members to the first and second side frames. Thus, when connecting the vehicle body frame connection member, which is a casting, to the first and second side frames, there are no restrictions to the degree of freedom for the components contained in the connection member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a vehicle body frame structure according to one embodiment of the present invention. 
         FIG. 2  is a perspective view showing a connection member of  FIG. 1 , in particular, a portion facing the inner side of a vehicle. 
         FIG. 3  is a perspective view showing a connection member of  FIG. 1 , in particular, a portion facing the outer side of the vehicle. 
         FIG. 4  is a view showing a vehicle structure near the connection member at the inner side of a side frame of  FIG. 1 . 
         FIG. 5  is a schematic view showing a cargo bend mounted on the vehicle body frame of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of a vehicle body frame connection member and a vehicle body frame structure according to the present embodiment will now be described with reference to  FIGS. 1 to 5 . 
     Referring to  FIG. 1 , a vehicle body frame  10  of a vehicle on which a cargo bed  61  is mounted includes two side frames  11 , a left one and a right one extending in the front to rear direction of the vehicle, and a plurality of cross-members, which have the form of hollow tetragonal posts and connect the two side frames  11  in the widthwise direction of the vehicle. The cargo bed  61  is set and positioned on the upper surfaces of the two side frames  11  and then fixed to the vehicle body frame  10 . 
     The side frame  11  includes a front frame portion  15 , which has the form of a hollow tetragonal post and serves as a first side frame portion arranged toward the front of the vehicle from a rear wheel  13  of the vehicle, and a rear frame portion  16 , which has the form of a hollow tetragonal post and serves as a second side frame portion arranged toward the rear of the vehicle from the rear wheel  13 . Further, the side frame  11  includes a connection member  20  that connects the front frame portion  15  and the rear frame portion  16  and is located above an axle  18 , which connects the left and right rear wheels  13  to each other. 
     The connection member  20  is connected to the front frame portion  15  and the rear frame portion  16  so that an upper surface  15   a  of the front frame portion  15  is flush with an upper surface  16   a  of the rear frame portion  16 . Further, the connection member  20  includes a setting surface  23  formed to allow for mounting of the cargo bed  61  shown in  FIG. 5  and connect the upper surface  15   a  of the front frame portion  15  and the upper surface  16   a  of the rear frame portion  16  so that the upper surfaces  15   a  and  16   a  form a continuous flat surface. 
     Referring to  FIGS. 2 and 3 , the connection member  20  is a casting having reflective symmetry relative to a central surface in the front to rear direction of the vehicle. An interposing portion  21 , which is located between the front frame portion  15  and the rear frame portion  16 , is formed integrally with two fastening portions  41 , which are located at the two sides of the interposing portion  21  in the front to rear direction of the vehicle and fastened to the front frame portion  15  or the rear frame portion  16  by fasteners such as bolts and nuts. Among the two fastening portions  41 , the fastening portion  41  fastened to the front frame portion  15  serves as a first fastening portion, and the fastening portion  41  fastened to the rear frame portion  16  serves as a second fastening portion. Further, the connection member  20  of each side frame  11  includes an inner portion facing toward the other side frame  11  and an outer portion facing away from the other side frame  11 . 
     An interposing base plate  22 , which forms the interposing portion  21 , is flat and extends in the front to rear direction of the vehicle. The interposing base plate  22  is arranged so that its inner surface  22   a  faces toward an inner side of the vehicle and its outer surface  22   b  faces toward an outer side of the vehicle. The interposing base plate  22  includes an upper edge extending straight in the front to rear direction of the vehicle and a lower edge curved so that the central portion in the front to rear direction of the vehicle is near the upper end. 
     An upper wall  24  extends along the upper edge and projects from the inner surface  22   a  of the interposing base plate  22 . The upper wall  24  includes the setting surface  23 . A lower wall  26  extends along the lower edge and projects from the inner surface  22   a . The lower wall  26  includes a recessed surface  25 , which is an inwardly curved surface and served as an opposite surface to the setting surface  23 . The curved lower wall  26  includes a peak through which a threaded portion  26   a  extends. A bump stopper  60  is connected to the threaded portion  26 A. Two side walls  27  project from the inner surface  22   a  to connect the ends of the upper wall  24  and the ends of the lower wall  26  to each other. A central portion of each of the two side walls  27  between the upper wall  24  and the lower wall  26  are curved toward the interposing base plate  22 . Two vertical ribs  28  connecting the upper wall  24  and the lower wall  26  are arranged at the inner side of the two side walls  27  in the front to rear direction of the vehicle. 
     Two threaded portions  31  are formed in the vicinity of each of the two fastening portions  41  in a location surrounded by the upper wall  24 , the lower wall  26 , the side wall  27 , and the vertical rib  28 . The fastening portions  41  are for fastening an upper bracket  58  that supports a shock absorber  57 . 
     A flat reinforcement rib  35  upwardly extends from an edge at the side of the setting surface  23  corresponding to the outer surface  22   b  of the interposing base plate  22  (outer edge corresponding to the outer portion). The reinforcement rib  35  includes an upper edge that is curved so that the height from the setting surface  23  increases as the central portion in the front to rear direction of the vehicle becomes closer. More specifically, the upper edge of the reinforcement rib  35  is curved so that the height from the setting surface  23  increases as the distance between the setting surface  23  and the recessed surface  25  decreases at locations along the outer edge of the setting surface. 
     Further, the reinforcement rib  35  is formed so that an inner surface  35   a  of the reinforcement rib  35  is orthogonal to the setting surface  23  of the upper wall  24  and so that the inner surface  35   a  of the reinforcement rib  35  is arranged toward the outer side of the vehicle from the frame portions  15  and  16 . 
     A peripheral wall  36  projects from an outer surface  35   b  of the reinforcement rib  35  and extends along the upper edge and side edges of the reinforcement rib  35 . The peripheral wall  36  extends to the outer surface  22   b  of the interposing base plate  22  at the side edges of the reinforcement rib  35  to as to fill the step between the outer surface  35   b  of the reinforcement rib  35  and the outer surface  22   b  of the interposing base plate  22 . Two vertical ribs  37 , which downwardly extend from the peripheral wall  36 , project from the outer surface  35   b  of the reinforcement rib  35  at locations in the outer surface  35   b  corresponding to where the vertical ribs  28  are arranged on the inner surface  22   a  of the interposing base plate  22 . The vertical ribs  37  extend to the outer surface  22   b  of the interposing base plate  22  to fill the step between the outer surface  35   b  of the reinforcement rib  35  and the outer surface  22   b  of the interposing base plate  22 . 
     Fastening base plates  42 , which form the fastening portions  41  formed integrally with the two sides of the interposing portion  21  in the front to rear direction of the vehicle, are continuous with the interposing base plate  22 . Each fastening base plate  42  is a rectangular plate that is inclined so that the upper edge of the fastening base plate  42  becomes closer to the lower edge at locations farther from the interposing base plate  22 . 
     An upper wall  44 , which is continuous with the upper wall  24  of the interposing portion  21 , extends along the upper edge of the fastening base plate  42  and projects from an inner surface  42   a  of the fastening base plate  42 . Further, a lower wall  46 , which is continuous with the lower wall  26  of the interposing portion  21 , extends along the lower edge of the fastening base plate  42  and projects from the inner surface  42   a . A bolt insertion portion  48 , including an insertion hole  47 , projects from each corner in the inner surface  42   a  of the fastening base plate  42 . Bolts are inserted through the insertion holes  47  to fasten the connection member  20  to the frame portions  15  and  16 . A circular through hole  49  is formed in a central portion of the rectangular and flat fastening base plate  42 . 
     The operation of the vehicle body frame  10  including the connection member  20  will now be described with reference to  FIGS. 4 and 5 . 
     As shown in  FIG. 4 , the connection member  20  is fastened to the front frame portion  15  by fastening members (not shown) under a situation in which one of the fastening portions  41  is received in the front frame portion  15 . Further, the connection member  20  is fastened to the rear frame portion  16  by fastening members (not shown) under a situation in which the other fastening portion  41  is received in the rear frame portion  16 . The connection member  20  is arranged above the axle  18  that extends in the widthwise direction of the vehicle and connects the left and right rear wheels  13 . 
     A spring bracket  51  is fixed to the front frame portion  15 . A shackle  52  is connected to the rear frame portion  16  and pivotal in the front to rear direction of the vehicle. A leaf spring  53  extends between the spring bracket  51  and the shackle  52 . When the leaf spring  53  is held between the axle  18  and a U-bolt seat  54 , a U-bolt  55  is connected to the U-bolt seat  54 . 
     Further, the shock absorber  57  is arranged in an area between the side frame  11  and the rear wheel  13 . An upper bracket  58  and a lower bracket  59  support the shock absorber  57 . The upper bracket  58  is fixed to the two threaded portions  31  located near the rear frame portion  16  in the connection member  20 . The lower bracket  59  is fixed to the axle  18 . Thus, the axle  18  vertically moves relative to the side frame  11  while the leaf spring  53  and the shock absorber  57  absorb vibration of the rear wheel  13  produced in accordance with the road surface along which the vehicle is driven. 
     The connection member  20 , which is located above the axle  18 , includes the recessed surface  25 , which is curved toward the upper surface of the side frame  11 . This allows the area surrounded by the recessed surface  25  to serve as a portion of the movable range of the axle  18 . Thus, the upper surface  15   a  of the front frame portion  15 , the upper surface  16   a  of the rear frame portion  16 , and the upper surface of the side frame  11  that is a flat surface formed by the setting surface  23  of the connection member  20  may be arranged closer to the axle  18 . The bump stopper  60  is connected to the threaded portion  26 A formed in the lower wall  26  of the connection member  20 . 
     Further, as shown in  FIG. 5 , the upper surface of the side frame  11  is flat. Thus, the cargo bed  61  mounted on the vehicle body frame  10  includes a wheel well  62  that is large enough to accommodate the rear wheel  13 . 
     As described above, the vehicle body frame  10  includes the advantages listed below. 
     (1) The connection member  20 , which connects the front frame portion  15  and the rear frame portion  16 , is located above the axle  18 , which connects the left and right rear wheels  13 , and includes the recessed surface  25 , which is recessed toward the setting surface  23  and away from the axle  18 . Further, the connection member  20  includes the setting surface  23  that connects the upper surface  15   a  of the front frame portion  15  and the upper surface  16   a  of the rear frame portion  16  to form a continuous flat surface. 
     This allows the area surrounded by the recessed surface  25  to serve as a portion of the movable range for the axle  18 . Thus, the upper surface of the side frame  11  may be arranged closer to the axle  18 . As a result, the cargo bed  61 , which is mounted on the vehicle body frame  10 , may be lowered. Further, due to the flat upper surface of the side frame  11 , which includes the front frame portion  15 , the rear frame portion  16 , and the connection member  20 , the wheel well  62  only needs to be large enough to accommodate the rear wheel  13  in the cargo bed  61  mounted on the vehicle body frame  10 . Thus, compared to when accommodating a portion of the side frame  11  in addition to the rear wheel  13 , the cargo capacity of the cargo bed  61  between the wheel wells  62  may be increased. Consequently, the cargo capacity of the lowered cargo bed  61  may be further increased. 
     (2) The lengths of the front frame portion  15  and the rear frame portion  16  may be freely set based on the connection member  20 , which is located above the axle  18 . Thus, in comparison with an integrally cast side frame, the degree of freedom for the side frame length is improved. 
     (3) The interposing portion  21  of the connection member  20  includes the reinforcement rib  35 , which is arranged toward the outer side of the vehicle from the front frame portion  15  and the rear frame portion  16  and which upwardly projects from an outer edge of the setting surface  23 . Thus, in addition to increasing the mechanical strength of the interposing portion  21 , the reinforcement rib  35  may be used as a positioning member for the cargo bed  61  that is mounted on the vehicle body frame  10  so that displacement of the cargo bed  61  when mounted on the vehicle body frame  10  is limited in the widthwise direction of the vehicle. 
     (4) In a connection member that does not include the reinforcement rib  35 , the mechanical strength easily decreases as the distance between the setting surface  23  and the recessed surface  25  decreases at locations along the outer edge of a setting surface. In this regard, the height of the reinforcement rib  35  from the setting surface  23  increases as the length of the interposing base plate  22  in the vertical direction at locations along the outer edge of the setting surface  23  decreases, that is, as the distance between the setting surface  23  and the recessed surface  25  decreases. As a result, the mechanical strength may be effectively compensated for at locations where the mechanical strength tends to decrease due to the formation of the recessed surface  25  in the connection member  20 . 
     (5) Generally, to allow for satisfactory welding to another member, there are many limitations to the components that may be contained in a casting. In this respect, in the present embodiment, the connection member  20 , which is a casting, includes the fastening portions  41 , which are fastened by fastening members such as bolts and nuts to the front frame portion  15  and the rear frame portion  16 . Thus, when connecting the connection member  20 , which is a casting, to the front frame portion  15  and the rear frame portion  16 , there are no restrictions to the degree of freedom for the components contained in the connection member  20 . 
     (6) When fastening the fastening portions  41  to the frame portions  15  and  16  with fastening members, the tightening of the fastening members applies stress to the fastening base plates  42 . However, the through hole  49 , which is formed in the central portion of the fastening base plate  42  allows for the stress to be dispersed. 
     The above embodiment may be modified as described below. 
     The connection member is not limited to a casting and may be formed by welding, for example, a plurality of steel materials. In this manner, the connection member  20  only needs the setting surface  23 , which connects the upper surface  15   a  of the front frame portion  15  and the upper surface  16   a  of the rear frame portion  16  so that the upper surfaces  15   a  and  16   a  form a continuous flat surface, and the recessed surface, which forms a movable area for the axle  18 . Further, the method for manufacturing the connection member  20  is not limited to casting. 
     The method for connecting the connection member to the front frame portion  15  and the rear frame portion  16  is not restricted to the fastening method using fastening members and may be a method that performs welding or the like for the connection. 
     The reinforcement rib  35  may have a height from the setting surface  23  that is constant, for example. In other words, the height of the reinforcement rib  35  from the setting surface  23  may be specified regardless of the distance between the setting surface  23  and the recessed surface  25 . 
     The lower edge of the interposing base plate  22  only needs to be recessed toward the upper edge at a central portion in the front to rear direction of the vehicle and does not have to be curved. That is, the recessed surface does not have to be an inwardly curved surface and only needs to be recessed toward the setting surface  23 . For example, the recessed surface may be formed by a plurality of flat surfaces. 
     The upper bracket  58 , which supports the shock absorber  57 , may be fixed to the front frame portion  15  or the rear frame portion  16  instead of the connection member  20 . Such a structure allows for the threaded portion  31  to be omitted from the connection member  20 .