Abstract:
A suspension bar assembly for an automotive vehicle includes a suspension bar having a bushing, a bushing retainer that exerts radially and axially compressive forces onto the bushing such that the bushing is in frictional engagement with the suspension bar, thereby preventing relative movement of the bushing and the suspension bar, and a mounting bracket that is adapted to connect the suspension bar to the automotive vehicle. A method of inducing a pre-load onto a bushing that supports a bar includes: providing a bar, placing a bushing onto the bar, placing a bushing retainer onto the bushing, and compressing the bushing axially and radially within the bushing retainer.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Technical Field  
           [0002]    The present invention generally relates to a stabilizer bar for an automotive vehicle. More specifically, the present invention relates to the mounting of bushing onto a stabilizer bar that produces a frictional engagement between the bushing and the stabilizer bar as well as between the bushing and the bushing retainer.  
           [0003]    2. Description of the Prior Art  
           [0004]    In an automotive vehicle, a stabilizer bar helps to keep the vehicle level, particularly when the vehicle is traveling through a curve. The ends of the stabilizer bar are connected to the right and left wheel assemblies of the vehicle. A pair of brackets, positioned between the ends of the stabilizer bar, secure the stabilizer bar to a structural component of the vehicle. Rubber bushings positioned between the stabilizer bar and the brackets provide limited torsional, axial and radial movement of the stabilizer bar relative to the bracket. The rubber bushings also dampen the movement of the stabilizer bar. Accordingly, the stiffness, or spring rate, of the bushings affects the feel of the suspension of the vehicle.  
           [0005]    To keep the bushings positioned on the stabilizer bar, a stop is usually formed within, or mounted onto, the stabilizer bar. Sometimes the stops are provided as an annular rib, or ribs, extending around the stabilizer bar. This makes the stabilizer bar more difficult to manufacture and adds weight to the stabilizer bar. Alternatively, the bushings can be secured in position on the stabilizer bar by using a chemical bonding agent. This, again, adds cost and complexity to the manufacturing process.  
           [0006]    Because the stiffness of the bushing affects the vehicle dynamics, bushings having different stiffness are used in different vehicles. This requires the warehousing of different bushings to provide the varying stiffness needed for different vehicles. Further, after time the bushings loose some resiliency, thereby causing the feel of the suspension in the vehicle to change. In order to repair this condition, the bushing would typically have to be replaced, at significant cost.  
           [0007]    A principle object of this invention is to provide a stabilizer bar assembly that utilizes common components, yet is able to provide varying stiffness for different vehicle applications.  
           [0008]    It is also an object of this invention to provide a stabilizer bar assembly having bushings which frictionally engage the stabilizer bar to keep the bushings in position on the stabilizer bar, wherein the bushings are axially compressed onto the stabilizer bar such that the stiffness of the bushing can be adjusted by varying the axial force at which the bushing is compressed.  
         SUMMARY OF THE INVENTION  
         [0009]    The disadvantages of the prior art are overcome by providing a stabilizer bar assembly, in accordance with the present invention, in which the stabilizer bar assembly includes a stabilizer bar having a bushing mounted thereon. The assembly further includes a bushing retainer that is in mechanical compressive engagement with the bushing such that the bushing is in frictional engagement with the stabilizer bar. A mounting bracket is adapted to connect the stabilizer bar to an automotive vehicle.  
           [0010]    In a first aspect of the present invention the bushing retainer exerts a radial force onto the bushing such that the bushing is compressed into frictional engagement with the stabilizer bar.  
           [0011]    In another aspect of the present invention, the bushing retainer exerts an axial compressive force onto the bushing such that the bushing is further compressed into frictional engagement with the stabilizer bar.  
           [0012]    Still another aspect of the present invention is a method of inducing a pre-load onto a bushing that supports a stabilizer bar including: providing a stabilizer bar, placing a bushing onto the stabilizer bar, placing a cylindrical bushing retainer, compressing the bushing axially and radially within the bushing retainer.  
           [0013]    Yet another aspect of the present invention is a method of inducing a pre-load onto a bushing that supports a stabilizer bar including: placing the bushing retainer about the stabilizer bar, injecting the bushing material, in a molten state, into the bushing retainer under pressure, and allowing the bushing material to cool and solidify within the bushing retainer.  
           [0014]    The aspects of the present invention provide a stabilizer bar assembly that uses common components, yet can be adjusted for different vehicle applications, and further, allows the bushing assemblies on the stabilizer bar to be repaired after the bushings have lost some of their resiliency. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a plan view of a stabilizer bar of the present invention;  
         [0016]    [0016]FIG. 2 is an enlarged view of the portion of the stabilizer bar shown in FIG. 1 enclosed by the circle numbered  2 ;  
         [0017]    [0017]FIG. 3 is a perspective view of a first preferred embodiment before an end cap has been placed to the bushing retainer;  
         [0018]    [0018]FIG. 4 is a sectional view taken along line  4 - 4  of FIG. 3;  
         [0019]    [0019]FIG. 5 is and end view of the first preferred embodiment after the end cap has been welded to the bushing retainer;  
         [0020]    [0020]FIG. 6 is a side sectional view of the first preferred embodiment after the end cap has been welded to the bushing retainer;  
         [0021]    [0021]FIG. 7 is a side sectional view of a variation of the first preferred embodiment wherein the bushing retainer has flanges adapted to hold the endcap thereon;  
         [0022]    [0022]FIG. 8 is and end view of the variation shown in FIG. 7 after the flanges have been deformed over the end cap to secure the end cap to the bushing retainer;  
         [0023]    [0023]FIG. 9 is a side sectional view of the variation shown in FIG. 7 after the flanges have been deformed over the end cap to secure the end cap to the bushing retainer;  
         [0024]    [0024]FIG. 10 is perspective view of a second preferred embodiment showing how inserts are placed within the bushing;  
         [0025]    [0025]FIG. 11 is a sectional view taken along line  8 - 8  of FIG. 7 after the inserts have been placed to the bushing;  
         [0026]    [0026]FIG. 12 is perspective view of a third preferred embodiment having fluid channels formed within the bushing;  
         [0027]    [0027]FIG. 13 is a sectional view taken along line  13 - 13  of FIG. 12;  
         [0028]    [0028]FIG. 14 is a sectional view taken along line  14 - 14  of FIG. 12;  
         [0029]    [0029]FIG. 15 is a sectional view of a fourth preferred embodiment prior to injecting the bushing material; and  
         [0030]    [0030]FIG. 16 is a sectional view similar to FIG. 15 after the bushing material has been injected. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    Referring to FIGS. 1 and 2, a stabilizer bar assembly for an automotive vehicle is shown generally at  10 . The stabilizer bar assembly  10  includes a stabilizer bar  12  with at least one bushing assembly  13  mounted thereon. The stabilizer bar  12  is generally made from steel, and can be solid or hollow. It is to be understood, that the stabilizer bar  12  can be made from other suitable materials. The bushing assemblies  13  include a bushing retainer  16  that encompasses a bushing  14  and is in mechanical compressive engagement with the bushing  14  such that the bushing  14  is frictionally engaged with the stabilizer bar  12 .  
         [0032]    The bushing  14  is made from an elastomeric material, such as rubber, or some other resilient material. Preferably, the bushing  14  is held onto the stabilizer bar  12  by friction alone. However, an adhesive can also be applied between the inner diameter of the bushing  14  and the stabilizer bar  12  to provide additional retention of the bushing  14  on the stabilizer bar  12 . Once the bushing  14  is properly located on the stabilizer bar  12 , the bushing retainer  16  is positioned about the bushing  14 . Referring to FIG. 4, the bushing retainer  16  is generally sleeve shaped having a cylindrical outer surface and a cylindrical passage extending therethrough defining an inner diameter. The inner diameter of the bushing retainer  16  is large enough to accommodate the bushing  14 .  
         [0033]    Referring to FIGS. 3 through 6, in a first preferred embodiment, the bushing retainer  16  includes a first end  18  and a second end  20 . The first end  18  is open, and the second end  20  provides an axial surface  22  which has an orifice  24  therethrough. The orifice  24  is adapted to receive the stabilizer bar  12 . An end cap  26  is in axially compressive engagement with the bushing  14  and is secured within the bushing retainer  16  adjacent the first end  18 . When the bushing assembly  13  is being assembled, the bushing retainer  16  is placed to the bushing  14  such that the bushing  14  rests against the axial surface  22  of the second end  20 , as shown in FIG. 4. The end cap  26  is brought into engagement with the bushing  14  and forced into the open first end  18  of the bushing retainer  16 , thereby compressing the bushing  14  therein. Once the bushing  14  is compressed to the desired stiffness, the end cap  26  is secured to the bushing retainer  16  to secure the compressed bushing  14  therein, as shown in FIGS. 5 and 6. As shown, the bushing assembly includes welds  28  to secure the end cap  26  within the bushing retainer  16 , however, it is to be understood that other methods of attachment could be used without departing from the scope of the present invention.  
         [0034]    Referring to FIGS. 7, 8, and  9 , in a variation of the first preferred embodiment the bushing retainer  16  includes a plurality of flanges  29  extending axially from the first end  18  of the bushing retainer  16 . The end cap  26  is brought into engagement with the bushing  14  and forced into the open first end  18  of the bushing retainer  16 , thereby compressing the bushing  14  therein. Once the bushing  14  is compressed to the desired stiffness, the flanges  29  are formed inward toward the shaft  12 , overlapping the end cap  26  to secure the end cap, as shown in FIGS. 8 and 9.  
         [0035]    Referring to FIGS. 10 and 11, in a second preferred embodiment, a bushing  30  includes longitudinal cavities  32  formed therein. A solid insert  34  is positioned within each of the longitudinal cavities  32  to further compress the bushing  30  within the bushing retainer  16 . Preferably, the inserts  34  have a cross sectional shape that closely matches the cross sectional shape of the longitudinal cavities  32 , only slightly larger. Because the inserts  34  are slightly larger, when the inserts  34  are inserted within the longitudinal cavities  32 , the inserts  34  will further compress the bushing  30  within the bushing retainer  16 , thereby increasing the frictional engagement of the bushing  30  and the stabilizer bar  12 .  
         [0036]    Referring to FIGS. 12, 13, and  14 , in a third preferred embodiment, the bushing  30  includes longitudinal cavities  32  formed therein. A fluid  36  fills each of the longitudinal cavities  32  to further compress the bushing  30  within the bushing retainer  16 . Preferably, the fluid  36  is injected into the longitudinal cavities  32  at a relatively higher pressure. The higher the pressure of the fluid  36  within the longitudinal cavities  32 , the more compressive force that is exerted upon the bushing  30  thereby increasing the frictional engagement between the bushing  30  and the stabilizer bar  12 .  
         [0037]    Referring to FIGS. 15 and 16, in a fourth preferred embodiment, a bushing retainer  38  includes an orifice  40 . The bushing retainer  38  is placed to the stabilizer bar  12  before the bushing  14 , and the bushing  14  is injected as a fluid into the bushing retainer  38 . Preferably, the molten bushing material is injected at pressure and allowed to cool and solidify within the bushing retainer  38 . Because the molten bushing material is pressurized when injected, the bushing  14  is under compression within the bushing retainer  38  after solidifying.  
         [0038]    Referring again to FIGS.  1 - 3 , a mounting bracket  42  is attached to the bushing retainer  16  to allow the bushing retainer  16  to be mounted to a structural component of the automobile. Preferably, the mounting bracket  42  includes mounting holes  44  that allow the mounting bracket  42  to be attached to the structure of an automobile. With the bushing  14  being made from a resilient material that allows limited movement of the stabilizer bar  12  relative to the bushing retainer  16 , the bushing assembly  13  provides a spring rate and dampening of the torsional, radial, and axial movement of the stabilizer bar  12  relative to the structure of the vehicle. As shown, the mounting bracket  42  is attached to the bushing retainer  16  on a bottom surface of the bushing retainer  16 . This version works well with light duty applications. For heavier duty applications, the mounting bracket  42  can extend over the top of the bushing retainer  16  to add strength to the assembly.  
         [0039]    One advantage of the present invention is that the same stabilizer bar assembly  10  can be used for applications requiring different spring rates within the bushings  14 . The effective spring rate of the bushings  14  will depend on the amount of compression that is exerted upon the bushing  14 . The same assembly  10  can have different spring rates by simply modifying the pressure at which the bushing  14  is compressed. If the stabilizer bar assembly  10  is to be put into a vehicle which requires a soft suspension feel, then the bushing  14  can be compressed such that the bushing  14  provides a soft feel. If the stabilizer bar assembly  10  is to be installed in a vehicle requiring a stiff suspension, then the bushing  14  can be compressed to a higher degree, thereby providing a stiffer feel to the suspension.  
         [0040]    Additionally, the stabilizer bar assembly  10  of the present invention will allow the bushings  14  to be repaired. Over time, as the bushings  14  loose some of their resiliency, their spring rate will change, causing the feel of the vehicle to change. In order to modify the spring rate, all that is required is to re-compress the bushing  14  to the desired compression pressure. This can be done by further compressing the bushing retainer  16  in the axial or radial direction, by injecting additional fluid  36  into the longitudinal cavities  32 , or replacing the inserts  34  within the longitudinal cavities  32  with larger inserts  34 . This will allow an older vehicle to have the suspension stiffness adjusted or repaired.  
         [0041]    It is to be understood, that the methods of the first three preferred embodiments can be used in combination. For example, the bushing  14  can be compressed by the end cap  26  after inserts  34  have been placed within the bushing  14 , or fluid  36  has been placed within cavities formed within the bushing  14 . Additionally, the invention has been described in terms of a stabilizer bar, however it is to be understood that the bushing assembly and the method of inducing the compressive forces within the bushing can be applied to other suspension components such as control arms, torsion arms, etc.  
         [0042]    The foregoing discussion discloses and describes four preferred embodiments of the invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that changes and modifications can be made to the invention without departing from the scope of the invention as defined in the following claims. The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.