Abstract:
The present apparatus and method relates to improvements in stiffening elements within a vehicle body structure at a sub-frame attachment point. In a first embodiment of the improved apparatus and method, a long mounting pin is used in combination with a generally planar shear bulkhead. The pin fits partially into a channel within the shear bulkhead. The pin is welded, near its bottom, to a sub-frame mounting bracket. The long mounting pin extends to the upper part of the vehicle frame and is also welded thereto. The shear bulkhead abuts a generally middle section of the mounting pin and two additional welds are placed securing the mounting pin to the shear bulkhead.

Description:
BACKGROUND OF THE INVENTION 
   In particular joints of a vehicle&#39;s suspension structure, stiffness and rigidity is desirable. One position where stiffness is desired is within the connection between the vehicle&#39;s rear sub-frame and the remainder of the vehicle body. Lack of stiffness in this joint is caused by the multi-component structure of the vehicle body adjacent to the connection point. Namely, the vehicle body is made of a combination of a sub-frame mounting bracket and a two part frame, the two parts being spaced apart and reinforced typically by a box-shaped internal bulkhead, as shown in  FIGS. 2-4 . In some vehicles, all of these parts are connected using a mounting pin which is projection welded to the sub-frame mounting bracket near the bottom of the pin (shown as crossed ovals) and MIG welded to the box-shaped internal bulkhead at the top of the pin. The box-shaped bulkhead is then welded to the upper part of the frame to complete the structure. Many welds are required to secure the joint. Namely, as illustrated in  FIG. 2 , the fore box bulkhead is spot welded (represented by black spots) to the frame in 12 places and the aft box bulkhead (not shown) in 10 places ( FIG. 3  also shows typical weld positions on the fore bulkhead). Two MIG welds (open circles) are used to attach each bulkhead to each mounting pin. 
   In another vehicle joint configuration (not illustrated), the mounting pin is a through-pin that is used to directly connect the sub-frame mounting bracket to the upper part of the frame, but does not utilize any type of bulkhead. However, neither of these configurations provides a joint that is overly stiff and many welds are required to form the complete joint. What is desired is an apparatus that provides increased stiffness in fore/aft, lateral, and vertical directions in the vehicle body adjacent to the sub-frame connection point and that is simply installed with fewer welds. 
   BRIEF SUMMARY OF THE INVENTION 
   The present apparatus and method relate to an improvement in the means for securing elements within a vehicle body structure at a sub-frame attachment point. In a first embodiment of the improved apparatus and method, a long mounting pin is used and the box-shaped internal bulkhead is replaced with a shear, generally planar, bulkhead. The mounting pin is projection welded to the sub-frame mounting bracket of the body in the same position as other designs. The long mounting pin extends to the upper part of the frame of the body and is MIG welded thereto. The shear bulkhead includes a channel running from a bottom edge to a top edge, and a generally middle section of the mounting pin fits at least partially into this channel. Two additional MIG welds are used to secure the mounting pin at its generally middle section to the shear bulkhead. Additionally, the shear bulkhead is spot welded on each of its sides to the upper part of the frame and/or the lower part of the frame. 
   In a second embodiment of the improved apparatus and method, a mounting pin having a shorter length than the pin in the first embodiment is projection welded to the sub-frame mounting bracket. A shear bulkhead is again used between the upper and lower parts of the frame, but is taller than the shear bulkhead in the first embodiment of the apparatus. The shear bulkhead is MIG welded on its top to the upper part of the frame and is spot welded on its sides to the upper or lower part of the frame. Again, the mounting pin fits at least partially into a channel running from the bottom edge to the top edge of the shear bulkhead. The mounting pin is MIG welded to the shear bulkhead at a point above the generally middle section of the mounting pin. 
   The present apparatus and method improves the distribution of vehicle load to the frame and body. Also, improvements are made in fore-aft, lateral, and vertical stiffness in the overall sub-frame vehicle body joint. Compared to other devices, a smaller bulkhead is used in the present apparatus and method, thus, improving stiffness while decreasing vehicle weight. Additionally, the vehicle load is distributed through fixation points to three areas on the pin (bottom, generally middle and top) as opposed to just the bottom and top as in other devices. As a result, local loads are better resisted. 
   The shear bulkhead works especially well to improve vertical stiffness because instead of a pin applying a point load to a bulkhead as in other devices, a shear load is applied. The load is then distributed to the frame by the shear bulkhead. The resistance to fore/aft and lateral loads is improved by using the entire frame (upper and lower parts) cross-section versus the prior design only using the small cross-section of the internal bulkhead and lower frame section. 
   The apparatus is also installed using fewer welds than what are used in other devices. Typically in the other devices  22 , spot welds and 4 MIG welds are required per sub-frame side. In the present apparatus and method, only 7 spot welds and 7 MIG welds are required per side of the sub-frame. These and other aspects of the apparatus and method are herein described in particularized detail with reference to the accompanying figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic side view of a vehicle showing generally the vehicle frame and a sub-frame attachment point; 
       FIG. 2  is a perspective view of an attachment apparatus of others; 
       FIG. 3  is another perspective view of an attachment apparatus of others; 
       FIG. 4  is a cross sectional view of an attachment apparatus of others; 
       FIG. 5  is a schematic view of an attachment apparatus including both embodiments and the vehicle frame; 
       FIG. 6  is a perspective view of a first embodiment of applicant&#39;s attachment apparatus; 
       FIG. 7  is a cross sectional view of the attachment apparatus of the first embodiment; 
       FIG. 8  is a perspective view of an attachment apparatus of a second embodiment; 
       FIG. 9  is a cross sectional view of the attachment apparatus of the second embodiment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings, specifically  FIGS. 1 ,  6  and  7 , a preferred sub-frame attachment apparatus  10  is illustrated. As described in more detail below, the attachment apparatus  10  includes a pin  12  and a shear bulkhead  14  that provide the necessary stiffness at a sub-frame connection point on the vehicle&#39;s rear frame, within the vehicle body frame elements, namely an upper part of the frame  22 , a lower part of the frame  20 , and a sub-frame mounting bracket  18 . Thus, an improved joint between the vehicle body and rear sub-frame  90  may be formed. 
   Referring to  FIGS. 6 and 7 , a portion of the rear frame  16  is shown and includes a lower part  20  and an upper part  22 . The lower part of the frame  20  includes a first flange  24  and a second flange  26 , a first sidewall  28 , a second sidewall  30  and a base  32 . The upper part  22  of the frame includes a first flange  34  and a second flange  36 , a first sidewall  38  and a second sidewall  40 , a first lateral portion  42  and a second lateral portion  44  and a channel  46 . 
   Within a preferred form of the lower part of the frame  20 , the base  32  is located between, and is generally perpendicular to, the first and second body sidewalls  28  and  30 . The body sidewalls  28  and  30  have generally equivalent heights. The base  32  joins each of the first and second sidewalls  28  and  30  at their bottom ends. The base  32  and sidewalls  28  and  30 , in combination, form an open topped duct. The base  32  also defines an aperture therein. The first flange  24  and second flange  26 , respectively, extend from the top end of each body sidewall  28  and  30  in a direction away from the inside of the duct. Each of the first and second flanges  24  and  26  is generally parallel to the base  32 . 
   Within a preferred form of the upper part of the frame  22 , the channel  46  is located between the first lateral section  42  and the second lateral section  44  and at a lower height than the lateral sections. The channel  46  includes a flat bottom  50  and angled sides  52 . The bottom  50  defines an aperture  54 . The angled sides  52  extend from the bottom  50  to the lateral sections  42  and  44  of the upper part of the frame  22 . The lateral sections  42  and  44  have equivalent widths and are generally parallel to the bottom  50  of the channel  46 . The first sidewall  38  is located on an opposite side of the first lateral section  42  from the channel  46 . Similarly, the second sidewall  40  is located on an opposite side of the second lateral section  44  from the channel  46 . The sidewalls  38  and  40  are generally planar, but are curved at their upper and lower ends. Each sidewall  38  and  40  is generally perpendicular to the adjacent lateral section  42  and  44 . The first flange  34  of the upper part of the frame  22  extends from the opposite end of the first sidewall  38  as the first lateral section  42 , extends in an opposite direction compared to the first lateral section  42 , and is generally parallel to the first lateral section  42 . The second flange  36  of the upper part of the frame  22  extends from the opposite end of the second sidewall  40  as the second lateral section  44 , extends in an opposite direction compared to the second lateral section  44 , and is generally parallel to the second lateral section  44 . 
   The sub-frame mounting bracket  18  includes a generally flat base  56  and at least one side wall  58  that is generally perpendicular to the base  56 . The flat base  56  defines an aperture therein. 
   The mounting pin  12  is preferably formed from round stock and includes a top end  60 , a generally middle section  62 , and a bottom end  64 . The bottom end  64  is beveled around its circumference  66 . The pin  12  includes a collar  68  located approximately one quarter of the way between the bottom end  64  and top end  60 . The collar  68  has an outer edge  70  that is beveled. 
   Referring to  FIGS. 5-7 , the shear bulkhead  14  is a generally planar element that includes generally perpendicular flanges at its top, bottom and side edges. The top flange  72 , bottom flange  74 , and at least one of the side flanges  76  and  78  preferably extend from the shear bulkhead  14  in a common direction which is away from the mounting pin when the apparatus  10  is assembled. The shear bulkhead  14  also includes an indented channel  80  (not in the same plane with the rest of the bulkhead) that extends from the bottom edge of the shear bulkhead  14  to the top edge. The channel  80  has a rounded configuration. The shear bulkhead  14  is shaped to fit within the surrounding frame  16 . In a preferred first embodiment shown in  FIGS. 6 and 7 , the shear bulkhead  14  is symmetrical and is wider at its top than at its bottom. The shape of the shear bulkhead is limited somewhat by the constraints of the frame shape. The flanges add stiffness to the shear bulkhead. In a variation of the first embodiment, the bulkhead on one side of the channel  80  has a greater surface area than on the opposite side. 
   Referring to  FIG. 1 , the rear sub-frame  90 , a portion of which is illustrated, is attached to the vehicle body  92  in four positions (only one position is shown). In each position, a mounting pin  12  and shear bulkhead  14  are used to provide the requisite stiffness in the vehicle body  92  at the attachment point  96 . 
   Referring to  FIGS. 6 and 7 , the attachment apparatus  10  is assembled by placing the shear bulkhead  14  within the upper and lower parts of the frame  20  and  22 . The side flanges  76  and  78  of the shear bulkhead  14  are spot welded (shown by shaded spots) to the lower part of the frame  20 . Depending on the size of the side flanges, one or two welds are required per flange. The mounting pin  12  is then inserted into the frame  16  through the hole in the base  32  of the lower part of the frame  20 . The mounting pin  12  is advanced until it reaches the top of the upper part of the frame  22 . Preferably, a portion of the mounting pin  12  extends through the aperture  54  in the upper part  22  of the frame. The sub-frame mounting bracket  18  is then placed over the bottom end of the mounting pin  12  and advanced until contact with the collar  68  on the mounting pin  12  is made. The mounting pin  12  is MIG welded (shown by hollow ovals) near its top to the channel  46  of the upper part of the frame  22 . The mounting pin  12  is MIG welded at its generally middle section  62  to the channel  80  in the shear bulkhead  14 . The mounting pin  12  is projection welded (shown by crossed ovals) just below its collar  68  to the sub-frame mounting bracket  18 . The upper and lower parts  20  and  22  of the frame are also welded together as known in the art. 
   Referring to  FIG. 1 , at the sub-frame attachment points  96 , a portion of the sub-frame  90  includes an aperture fitted with a bushing and the bushing is pushed over the lower end  98  of the mounting pin  12 . A bolt (not shown) is then secured to the mounting pin  12  in order to hold the sub-frame  90  to the frame  92 . 
   Referring to  FIGS. 8 and 9 , a second embodiment of the apparatus is shown. Elements that are the same as within the first embodiment are referred to with the same reference numbers. 
   The mounting pin  112  of the apparatus  110  is preferably formed from round stock and includes a top end  160 , a generally middle section  162 , and a bottom end  164 . The mounting pin  112  within the second embodiment of the apparatus is shorter than the mounting pin  12  in the first embodiment of the apparatus. The bottom end  164  is beveled around the circumference  166 . The pin  112  includes a collar  168  located about one quarter of the way between the bottom end  164  and top end  160 . The collar  168  has an outer edge  170  that is beveled. 
   The shear bulkhead  114  is a generally planar element that includes perpendicular flanges at its top, bottom and side edges. The top flange  172 , bottom flange  174 , and side flanges  176  and  178  preferably all extend from the shear bulkhead  114  in a common direction. The shear bulkhead  114  also includes a weld tab  173  extending from the top flange  172 . The shear bulkhead  114  also includes an indented channel  180  that extends from the bottom edge of the shear bulkhead  114  to the top edge. The shear bulkhead  114  of the second embodiment is taller than the shear bulkhead  14  of the first embodiment of the apparatus and is shaped to fit within the surrounding frame  16 . Within the second embodiment, the shear bulkhead  114  preferably has a width that is more narrow at is bottom than at its generally middle section and top, although other shapes are possible as shown in  FIG. 5 . Additionally, the width of the shear bulkhead is preferably narrower at the top than at its generally middle section. 
   Referring to  FIGS. 8 and 9 , the attachment apparatus  110  is assembled with the shear bulkhead  114  placed inside of the upper and lower parts of the frame  16 . The shear bulkhead  114  extends up to the lower side of the first and second transverse portions  42  and  44  of the upper part of the frame  22 . The side flanges  176  and  178  are spot welded to the sides of the upper or lower part of the frame and the welding tab  173  is MIG welded to the upper part of the frame  22 . The mounting pin  112  is then slid into the hole in the base of the lower part of the frame  20  and advanced until the top of mounting pin  112  has reached about three quarters of the height of the shear bulkhead  114 . The mounting pin  112  fits into the channel  180  of the shear bulkhead  114 . The mounting pin  112  is then MIG welded to the shear bulkhead  114  above the generally middle section  162  of the mounting pin  112 . The sub-frame mounting bracket  18  is then placed over the lower end of the mounting pin  112  and moved toward the frame  16  until the collar  168  on the mounting pin stops upward movement. The mounting pin  112  is then projection welded just below the collar  168  to the sub-frame mounting bracket  18 . 
   Referring to  FIG. 1 , an apparatus of the first embodiment is used where the front part of the rear sub-frame attaches to the vehicle and an apparatus of the second embodiment attaches to the rear part of the rear sub-frame of the vehicle. 
   In the first embodiment, several different configurations of the frame are possible depending upon the location of the connection point on the vehicle body. Each configuration though has at least an upper surface that defines an aperture whereby the mounting pin is welded to the upper part of the frame adjacent to the aperture. Additionally, each configuration of the frame has two side surfaces whereby the side flanges on the shear bulkhead are welded to the frame side surfaces. Correspondingly, the shear bulkhead  14  has varying shapes because the shear bulkhead shape matches, in general, the shape of the inside of the frame. 
   Also, in the second embodiment, several different configurations of the frame are possible depending upon location on the vehicle body. Each configuration of the frame, though, has at least a generally flat surface whereby the welding tab on the shear bulkhead is weldable to this flat surface of the upper part of the frame. Additionally, each configuration of the frame has two side surfaces whereby the side flanges on the shear bulkhead are weldable to the side surfaces. 
   In the first and second embodiments, several different configurations of the sub-frame mounting bracket are possible depending upon the location on the vehicle body. Each configuration though has at least a flat surface that defines an aperture whereby the mounting pin is welded to the flat surface just below the mounting pin collar. 
   In the first and second embodiments, alternatively, either a round mounting pin or hex mounting pin may be used. A portion of, or the entire mounting pin may be hollow. 
   Although the apparatus and method have been shown and described with reference to certain preferred and alternate embodiments, the apparatus and method are not limited to these specific embodiments. Minor variations and insubstantial differences in the various combinations of materials and methods of application may occur to those of ordinary skill in the art while remaining within the scope of the apparatus and method as claimed and equivalents.