Abstract:
A vehicle rear body structure has left and right gussets for coupling left and right damper mounting portions and a floor cross member. The left and right damper portions serve as component parts on which left and right dampers are mounted to mitigate impacts transmitted from left and right rear wheels and hence is required to have increased strength. The left and right damper mounting portions are coupled to the floor cross member with high rigidity via the left and right gussets and are so reinforced.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a vehicle rear body structure configured to prevent a decrease in axial strengths of fixture bolts for rear-wheel dampers and to increase workability in tightening the dampers and a damper-mounting-portion reinforcing member together to damper mounting portions.  
         BACKGROUND OF THE INVENTION  
         [0002]    A conventional vehicle rear body structure is exemplified in FIGS. 9 and 10 hereof. In FIG. 9, wheel houses  101 ,  102  which accommodate left and right rear wheels are located at left and right sides of a rear floor panel  100 . Damper mounting portions  103 , 104  are located at routs or joints of the wheel houses  101 ,  102  for mounting left and right dampers  108 ,  109  to mitigate impacts or shocks transmitted from the rear wheels and to support the rear wheels. A reinforcement bar  105  serving as a damper-mounting-portion reinforcing member is arranged to extend between the damper mounting portions  103 ,  104  to allow the damper mounting portions  103 ,  104  to have increased rigidity. Reference numeral  107  designates a concave section for storing a spare tire. The reinforcement bar  105  is comprised of terminal metal fixtures  111 ,  112  secured to the damper mounting portions  103 ,  104 , respectively, and a bar  113  unitarily coupled to the terminal metal fixtures  111 ,  112 .  
           [0003]    As shown in FIG. 10, both ends of the reinforcement bar  105  are tightened to the damper mounting portions  103 ,  104  together with the dampers. The terminal metal fixtures  111 ,  112  of the reinforcement bar  105  have pluralities of bolt insertion bores  114 ,  115 , respectively. Fitting a plurality of bolts  116  provided at upper distal ends of respective dampers into associated mounting bores, not shown, which are formed in the damper mounting portions  103 ,  104 , upward from a rear side to allow the bolts  116  to pass through the bolt insertion bores  114 ,  115  of the terminal metal fixtures  111 ,  112 , respectively, permits a nut, not shown, to be screwed onto each of the bolts  116 .  
           [0004]    Since the reinforcement bar  105  has mounting pitches P 1 , P 2  (i.e., distances between bolts  116 ,  116  of the left and right dampers) which are substantially equal to a distance between the left and right wheels, such a structure suffers from an issue of increased manufacturing errors in the distance between the bolt insertion bore  114  and the bolt insertion bore  115 . In order to absorb the manufacturing errors, the insertion bores  114 ,  114  for either ones of the left and right bolts are formed in elongated apertures.  
           [0005]    Thus, the presence of the bolt insertion bore  114  formed in the elongated aperture causes a seating surface, which bears a nut to be screwed onto the bolt  116 , to have a decreased surface area with a resultant increase in surface pressure acting on the seating surface when rotating the nut to be tightened with a given tightening torque. It seems that excessively higher the surface pressure of the seating surface, the lower will be the axial strength of the bolt due to deformation in the seating surface.  
           [0006]    When tightening both the dampers  108 ,  109  and the reinforcement bar  105  together to the damper mounting portions  103 ,  104 , mounting work must be initially carried out for mounting the terminal metal fixture  111  of the reinforcement bar  105  together with the dampers  108 ,  109  in an unsteady condition wherein the terminal metal fixture  112  of the reinforcement bar  105  is merely placed on the one-side damper mounting portion  104 . This results in displacement of the terminal fixture  111  during the mounting operation to cause troublesome work in mounting the terminal metal fixture  111 , resulting in deteriorated workability.  
         SUMMARY OF THE INVENTION  
         [0007]    It is therefore an object of the present invention to provide an improved vehicle rear body structure which suppresses deterioration in axial strength of mounting bolts for rear-wheel dampers while providing improved workability in tightening both dampers and a damper-mounting-portion reinforcing member to damper mounting portions.  
           [0008]    According to an aspect of the present invention, there is provided a vehicle rear body structure which comprises left and right damper mounting portions for mounting left and right dampers, which mitigate impacts transmitted from left and right rear wheels, to a vehicle body, respectively, a floor cross member disposed in the vicinity of the left and right damper mounting portions, and left and right gussets for coupling the left and right damper mounting portions and the floor cross member with respect to one another for reinforcing the left and right damper mounting portions.  
           [0009]    With such a vehicle rear body structure, the presence of a structure wherein the left and right damper mounting portions are connected to the floor cross member at areas in the vicinity of the damper mounting portions via the left and right gussets enables the left and right damper mounting portions to have increased rigidity while shortening the mounting pitch, according to the present invention, to a lower value than that of the reinforcement bar employed in the conventional practice, resulting in a decrease in errors in the mounting pitches. Consequently, for example, when tightening the dampers and the gussets together to the damper mounting portions, there is no need for the bores formed in the gussets to pass the mounting bolts, formed at the upper portions of the dampers, to be formed in a larger size than that of an outer diameter of the mounting bolt of the damper, enabling the seating surface of the gusset which bears the nut to be screwed onto the mounting bolt to have an increased surface area. Accordingly, it is possible to preclude a decrease in the axial strength of the mounting bolt of the damper even when increasing the tightening torque of the nut discussed above.  
           [0010]    Further, the damper and the gusset can be tightened together at the damper mounting portion under a condition where the gusset is mounted to the floor cross member, resulting in am improvement in the workability while enabling a productivity to be improved.  
           [0011]    In the vehicle body structure arranged in accordance with the present invention, connecting the above left and right gussets with the rod enables the rigidity of the left and right damper mounting portions to be further improved with favorable results.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    Certain preferred embodiments of the present invention will be described in more detail below, by way of example only, with reference to the accompanying drawings, in which:  
         [0013]    [0013]FIG. 1 is a perspective view of a vehicle body composed of a vehicle rear body structure according to a preferred embodiment of the present invention;  
         [0014]    [0014]FIG. 2 is a perspective view illustrating the vehicle rear body structure according to the present invention;  
         [0015]    [0015]FIG. 3 is a perspective view of a gusset shown in FIG. 2;  
         [0016]    [0016]FIG. 4 is a top plan view of the gusset shown in FIG. 3;  
         [0017]    [0017]FIG. 5 is an enlarged cross sectional view taken along line  5 - 5  of FIG. 2;  
         [0018]    [0018]FIG. 6 is a perspective view of a vehicle rear body structure illustrating an example wherein left and right gussets shown in FIG. 2 are coupled with a crossbeam  
         [0019]    [0019]FIG. 7 is an enlarged perspective view of the crossbeam shown in FIG. 6;  
         [0020]    [0020]FIG. 8 is an enlarged cross sectional view taken along line  8 - 8  of FIG. 6;  
         [0021]    [0021]FIG. 9 is a perspective view illustrating a conventional vehicle rear body structure; and  
         [0022]    [0022]FIG. 10 is a top plan view of a reinforcement bar shown in FIG. 9. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    Referring now to FIG. 1, there is shown a vehicle body composed of a vehicle rear body structure according to the present invention. The vehicle body  10  includes a frame structure comprised of a front body  11 , an underbody  12 , laterally spaced left and right sides bodies  13 ,  14 , a roof member  15  and a rear body  16 .  
         [0024]    The front body  11  has an engine space in which an engine is mounted while bearing inputs applied from front suspension units. The underbody  12  has a floor panel on which a passenger compartment and a luggage space are formed at areas rearward of the front body  1  while accommodating a fuel tank and a spare tire, etc. and further bearing inputs applied from rear suspension units. The left and right side bodies  13 , 14  rise upright from the respective sides of the underbody  12  to define side walls of the passenger compartment. The roof  15  extends between respective upper ends of the side bodies  13 , 14  to form a ceiling of the passenger compartment. The rear body  16  defines the luggage space at a rear part of the under body  12 .  
         [0025]    The underbody  12  includes a front floor panel  21  which constitutes a floor of the passenger compartment, a rear floor panel  22  which serves as a vehicle body rear section forming a floor of the luggage space, and a middle floor cross member  23  located in the vicinity of a junction between the front floor panel  21  and the rear floor panel  22 .  
         [0026]    The left side body  13  includes a front pillar  26  to which a door is hinged, a sill  27  mounted to the underbody  12  at a side thereof to increase rigidity of the body, and a center pillar  28 , adapted to support a rear edge of the door, to which component parts for locking the door are mounted. The right side body  14  includes a sill  31  and a center pillar  32  in a similar manner as the left side body  13 .  
         [0027]    [0027]FIG. 2 shows the vehicle rear body structure according to the present invention. A front portion of the rear floor panel  22  has a seat mounting section  35  on which the seat is mounted. A concave portion  36  for accommodating a spare tire is formed in the rear floor panel  22  at an area extending between a central portion and a rear part. Wheel houses  37 ,  38  for receiving left and right rear wheels  39 ,  39  shown in FIG. 1 are formed at left and right sides of the rear floor panel  22 . Damper mounting portions  41 , 42  are located in the rear floor panel  22  at areas close proximity to joints of the wheel houses  37 , 38  for the rear wheels  39 ,  39 , i.e., for mounting for example strut type dampers  40 ,  40 . A rear-floor upper cross member  43 , serving as a floor cross member, is joined to the rear floor panel  22  at areas close proximity to the damper mounting portions  41 ,  42 . The rear-floor upper cross member  43  extends in a widthwise direction of the vehicle. In order for the damper mounting portions  41 ,  42  to have increased rigidity, gussets  44 ,  45  are fixedly secured to the rear-floor upper cross member  43  and the respective damper mounting portions  41 ,  42 .  
         [0028]    The damper mounting portions  41 ,  42  serve as component parts which bear inputs, delivered from the rear suspensions, such as a pushup force, a fore and aft force and a vehicular widthwise force.  
         [0029]    The rear-floor upper cross member  43  is joined to the rear floor panel  22  to form a closed cross sectional area such that the rear floor panel  22  has an increased bending rigidity and twisting rigidity.  
         [0030]    [0030]FIGS. 3 and 4 show the left gusset  44  which forms one of the gussets  44 , 45  shown in FIG. 2.  
         [0031]    The gusset  44  includes a U-shaped terminal portion  51  adapted to be mounted to the damper mounting portion  41  shown in FIG. 2, bolt insertion bores  52 , 52  formed in respective distal ends of the U-shaped terminal portion  51 , a sidewise upright portion  53  adapted to be mounted to the rear-floor upper cross member  43  shown in FIG. 2, a bolt insertion bore  54  formed in the sidewise upright portion  53 , and a nut  55  and an upright segment  56  located in the vicinity of the bolt insertion bore  54 . The right gusset  45  shown in FIG. 2 has a shape symmetric with the left gusset  44  shown in FIG. 3 and, therefore, a detailed description of the same is herein omitted.  
         [0032]    In FIG. 4, reference character P designates a distance between each of the bolt insertion bores  52 ,  52  of the U-shaped terminal portion  51  and the bolt insertion bore  54  of the sidewise upright portion  53 , i.e., a mount pitch of the gusset  44  with respect to the damper mounting portions  41 ,  42 . The mounting pitch P is designed to have a shorter length than each of the mounting pitches P 1 , P 2  (see FIG. 10), resulting in a reduced unevenness in the mounting pitch P to permit the bolt insertion bores  52 ,  52  and the bolt insertion bore  54  to have round shapes, instead of elongated apertures, (which has a smaller value than the longitudinal axis of the conventional elongated aperture).  
         [0033]    As shown in FIG. 5, the rear-floor upper cross member  43  is secured to the rear floor panel  22 . The gusset  44  is mounted to the rear-floor upper cross member  43  by means of a nut  58 , with a reinforced plate  57 , and a bolt  61 . The nut  58  with the reinforced plate  57  is positioned inside the rear-floor upper cross member  43 . The reinforced plate  57  serves to reinforce the gusset mounting portion  44  of the rear-floor upper cross member  43 .  
         [0034]    A mounting condition between the damper mounting portion  41  and the gusset  44  shown in FIG. 2 will be described below in conjunction with FIG. 8 which will be discussed later.  
         [0035]    The vehicle rear body structure according to the preferred embodiment concerns a structure wherein the left and right damper mounting portions  41 ,  42  are jointed to the rear-floor upper cross member  43 , at the areas closer to the damper mounting portions  41 ,  42 , i.e., to the rear floor panel  22 , composed of the rigid portion, via the left and right gussets  44 ,  45  for thereby reinforcing the damper mounting portions  41 ,  42 . With the vehicle rear body structure configured in such a structure, the present invention enables the mounting pitch P of the gussets  44 ,  45  to be shorter than that of the reinforced bar employed in the prior art practice while increasing the rigidity of the left and right damper mounting portions  41 ,  42 , resulting in a minimized error in the mounting pith P.  
         [0036]    Accordingly, for example, when tightening both the dampers  40 ,  40  and the gussets  45 ,  45  to the damper mounting portions  41 ,  42 , since there is no need for each of the bolt insertion bores  52 ,  52 , formed in the gussets  44 , 45 , to have a larger diameter than each of fixture bolts  76  (which will be described below in detail) formed at upper ends of the respective dampers, it is possible for the gussets  44 , 45 , which bear nuts  77  (described in detail below) screwed onto the mounting bolts  76 , to have increased seating surface areas. As a consequence, even in the presence of an increased tightening torque produced by the nut  77 , the seating surface is not applied with an excessively large surface pressure to prevent deformation caused during tightening operation of the nut with respect to the seating surface and a resultant crumpled phenomenon caused after the tightening operation for thereby suppressing a decrease in an axial tightening force of the mounting bolt  76  of the damper.  
         [0037]    Further, the dampers  40 ,  40  and the gussets  44 ,  45  may be tightened together under a condition wherein the gussets  44 ,  45  are mounted to the rear-floor upper cross member  43 , resulting in improved workability while increasing mass production capability.  
         [0038]    Furthermore, the use of existing rear-floor upper cross member  43  for reinforcing the damper mounting portions  41 ,  42  with the gussets  44 ,  45  precludes the need for preparing component parts specific for mounting the gussets  44 ,  45  to the rear-floor upper cross member  22 , for thereby enabling the manufacturing cost of the vehicle body  10  (see FIG. 1) from being increased.  
         [0039]    [0039]FIG. 6 shows the vehicle rear body structure in a state wherein the left and right gussets  44 ,  45  of the preferred embodiment shown in FIG. 2 are connected to one another via a crossbeam  63  serving as a rod.  
         [0040]    Thus, the presence of the gussets  44 ,  45  on the rear-floor upper cross member  43  and the respective damper mounting portions  41 ,  42  while connecting the gussets  44 ,  45  with the crossbeam  63  enables the damper mounting portions  41 ,  42  and accordingly the rear body structure to have further increased rigidity.  
         [0041]    [0041]FIG. 7 shows the crossbeam shown in FIG. 6. The crossbeam  63  is composed of a steel pipe having both ends formed with respective flat portions  65 , with each flat portion  65  having lateral edges formed with upright ridges  66 ,  66  while one flat portion  65  having an elongated bolt insertion bore  67  and an elongated positioning bore  68  whereas the remaining other flat portion  65  is formed with a bolt insertion bore  71  in a round shape and a positioning bore in a round shape.  
         [0042]    As shown in FIG. 8, when connecting one end of the crossbeam  63  to the left gusset  44 , the upright segment  56  of the gusset  44  is fitted to the positioning bore  68  of the crossbeam  63  and the bolt  74  is inserted through the bolt insertion bore  67  of thecrossbeam  63 , with the bolt  74  being screwed into the nut  55  of the gusset  44 . Similarly, mounting the other end of the crossbeam  63  to the right gusset  45  (see FIG. 2) allows the left and right gussets  44 ,  45  to be interconnected to one another via the crossbeam  63 . Reference numerals  76 ,  77  designate the damper fixture bolt  76  and the nut  77  for tightening both the U-shaped terminal portion  51  of the gusset  44  and the damper mounting portion  41  with respect to one another. Reference numeral  78  designates a spacer secured to the damper mounting portion  41  by a projection welding.  
         [0043]    Thus, by connecting the left and right gussets  44 ,  45  to one another via the crossbeam  63 , the rigidity of the left and right damper mounting portions  41 , 42  are enabled to be further increased, with a resultant increase in the rigidity of the rear body structure.  
         [0044]    In FIG. 6, although there is shown an example wherein the left and right gussets are connected to one another via the crossbeam, the present invention may have a structure wherein an intermediate portion of the cross bean is designed to be further mounted to the rear-floor upper cross member.  
         [0045]    The present disclosure relates to the subject matter of Japanese Patent Application No. 2001-169761, filed Jun. 5, 2001, the disclosure of which is incorporated herein by reference in its entirety.