Abstract:
A vehicle stabilizer bar bushing assembly has an elastomeric bushing and a bushing liner. The bushing liner is internal to the bushing and is not bonded to the bushing prior to be assembled onto the vehicle stabilizer bar. Both the bushing and the bushing liner have ledges at the opposing edges of the structures, to limit movement of the bushing underneath a mounting bracket and to limit movement of the bushing over the bushing liner. The bushing liner is formed of a polymeric material having a relatively low coefficient of friction and is flexible to permit formation of non-linear configurations of the bushing liner.

Description:
[0001]    This application claims the benefit of, and incorporates by reference, U.S. Provisional Application No. 60/791,797 filed Apr. 13, 2006. 
     
     FIELD OF THE INVENTION 
       [0002]    The present invention is directed to a bushing for a vehicle stabilizer bar. More specifically, the present invention is directed to an improvement for a bushing assembly. 
       BACKGROUND OF THE INVENTION 
       [0003]    In automotive vehicles, a stabilizer bar is connected to the right and left wheel assemblies of a vehicle to assist in keeping the vehicle level. Typically, at least one metal bracket, positioned between the ends of the stabilizer bar, secures the stabilizer bar to a structural component of the vehicle. A rubber bushing is positioned between the stabilizer bar and the metal bracket to limit axial and radial movement of the stabilizer bar relative to the bracket. The rubber bushing also dampens the stabilizer bar movements. 
         [0004]    Conventional design of the vehicle suspension system permits rotation between the stabilizer bar and the bushing. However, slippage between the stabilizer bar and the bushing can create a slip-stick phenomenon between the metal and rubber materials, and may result in an audible noise, noticeable by the driver. To reduce the coefficient of friction between the stabilizer bar and the bushing, it has been known to provide the inner side of the bushing with a self-lubricating rubber or a secured liner or internal layer of polytetrafluoroethylene (PTFE) which is mostly commonly known as Teflon, high molecular weight polyethylene, or polyester. 
         [0005]    However, with a self-lubricating material, the coefficient of friction varies over temperature ranges, during bushing degradation, and with road contaminants. Teflon lined bushings may also delaminate during bushing degradation, reducing its effectiveness. 
         [0006]    Another concern in regards to stabilizer bars and bushings arises from the various configurations for stabilizer bars. The configuration of a stabilizer bar will typically include several bends; the exact configuration of the stabilizer bar is specific to the vehicle platform as it is configured to go around other features of the vehicle undercarriage. Because of the bends and variations of both the stabilizer bar and the vehicle undercarriage, which dictates where a bushing can be mounted, there may arise vehicle platforms where the bushing must be mounted where there is a bend in the stabilizer bar. Thus the bushing assembly, and the components thereof, must be flexible to accommodate the bar and permit the desired movement between the stabilizer bar and the bushing assembly. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention is directed to a stabilizer bar bushing assembly wherein the assembly includes an internal component that provides both a low coefficient of friction between the component and the stabilizer bar and is flexible to permit movement along bends of the stabilizer bar. 
         [0008]    The present invention is a vehicle stabilizer bar mounting assembly. The assembly has a retaining bracket, an elastomeric bushing, and a bushing liner. The bushing liner is internal to the bushing and the bracket is secured over an external surface of the bushing. The bushing has a generally torodial shape between a pair of opposing ends, a constant internal diameter, and ledges at the opposing ends. The bushing liner has a length greater than the bushing, a pair of opposing ends, liner ledges at the opposing ends, and is formed from a non-elastomeric material. When assembled, the liner ledges of the bushing liner extend past the ledges of the bushing and the liner ledges have an external diameter greater than the internal bushing diameter, and the bushing liner is not bonded to the bushing. 
         [0009]    In one aspect of the invention, the bushing liner is formed from a polymeric material having a coefficient of friction less than the coefficient of friction of the elastomer forming the bushing. 
         [0010]    In another aspect of the invention, the bushing liner is formed from a flexible material capable of being formed into non-linear configurations. 
         [0011]    In another aspect of the invention, the mounting bracket has an internal radius and the bushing ledges have an external radius greater than the mounting bracket internal radius. 
         [0012]    In another aspect of the invention, the mounting bracket has an internal radius and the bushing has a central compression area having an external diameter, the external diameter of the compression area being greater than the twice the internal radius of the mounting bracket. 
         [0013]    In another aspect of the invention, the bushing and the bushing liner have corresponding non-linear configurations. In such an embodiment, the mounting bracket may have a pair of securing arms, each arm having first and second ends, wherein the first ends of the arms having a mounting means located therein, and the second ends of the arms are joined to each other. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention will be described by way of example and with reference to the accompanying drawings in which: 
           [0015]      FIG. 1  is a stabilizer bar and a mounting assembly for the bar; 
           [0016]      FIG. 2  is a cross sectional view along section line  2 - 2  of  FIG. 1 ; 
           [0017]      FIG. 3  is a perspective view of the bushing, liner, and stabilizer bar; 
           [0018]      FIG. 4  is an alternative embodiment of a stabilizer bar and mounting assembly; 
           [0019]      FIG. 5  is an embodiment of the liner; and 
           [0020]      FIG. 6  is an alternative embodiment of the bushing, liner, and stabilizer bar. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    The following language is of the best presently contemplated mode or modes of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. The reference numerals as depicted in the drawings are the same as those referred to in the specification. For purposes of this application, the various embodiments illustrated in the figures each use the same reference numeral for similar components. The structures employ basically the same components with variations in location or quantity thereby giving rise to the alternative constructions in which the inventive concept can be practiced. 
         [0022]      FIGS. 1 and 2  illustrate a portion of a vehicle stabilizer bar  10  secured to a vehicle chassis or frame  12  by means of mounting assembly including a generally U-shaped metal retaining bracket  14 . The mounting bracket  14  is secured on both sides of the stabilizer bar to the vehicle chassis  12 . 
         [0023]    The mounting assembly includes a bar bushing  16  and a bushing liner  18 . The bar bushing  16  has a generally torodial shape and a slit along the length of the bushing  16  so that the bushing  16  may be mounted onto the stabilizer bar  10 . The bushing  16  has a constant internal radius R B  and a varying external configuration. The constant internal bushing radius R B  is greater than the outer radius R S  of the stabilizer bar  10  by not more than 5 mm, preferably not more than 3 mm. Radius values of the stabilizer bar  10  and elements of the mounting assembly are measured relative to the centerline CL of the stabilizer bar  10 , which corresponds to the centerline of the bushing  16  and liner  18 . 
         [0024]    The external configuration of the bushing  16  has a central compression area  20  and ledges  22  at the opposing ends of the bushing  16 , see  FIG. 3 . The central compression area  20  includes an area having a radius R BC  greater than the minimum radius R BMIN  of the external configuration. At least a portion of the central compression area has a radius R BC  greater than the radius R M  created by the mounting bracket. While the compression area  20  is illustrated as a single, hill-like projection, the external configuration of the compression area  20  is not limited to the illustrated design and may be formed with multiple projections or even have grooves therein. When provided with ledges, the ledges  22  at the bushing ends have a radius R BMAX  greater than the internal radius R M  of the mounting bracket. The ledges  22  prevent the bushing  16  from moving out from under the metal bracket  14 . 
         [0025]    Internal to the bushing  16  is a bushing liner  18 . The bushing liner  18  has a defined length with a generally hose-like configuration and ledges  24  at the opposing ends of the liner  18 . Similar to the bushing  16 , the liner  18  has a slit  26  to permit application of the liner onto the stabilizer bar  10 , see  FIG. 5 . The liner  18  has a length greater than the bushing  16  wherein, when the bushing  16  is positioned over the liner  18 , the bushing  16  is located between the opposing liner ledges  24 . The liner ledges  24  have a height H E  in range of 2 to 10 times the thickness H L  of the central portion of the liner  18 . The liner  18  has a constant internal radius R LI  corresponding to not more than 1 mm, preferably not more than 3 mm greater than the stabilizer bar external diameter. The central external radius of the liner  18  corresponds to the internal radius R B  of the bushing  16  within conventional engineering tolerances but also may be greater than R B  to create interference and a tighter fit to the assembly. Along the slit  26  of the liner  18 , the slit creates a pair of opposing longitudinal edges. At each longitudinal edge, a rib  28  may be provided, the ribs  28  may or may not have a height the same as the ledges  24 . When the liner  18  is provided with the ribs  28 , it creates an enclosed channel for the bushing  16  to sit in and assists in alignment of the bushing  16  on the liner  18 . 
         [0026]    The liner  18  is formed of a polymeric material having a low coefficient of friction and excellent abrasion resistance between the stabilizer bar  10  and the bushing  16 . The coefficient of friction for the liner  18  is less than the coefficient of friction of the elastomer forming the bushing  16 , the coefficients being that of friction against metal. Additionally, the liner  18  is formed of a flexible material to permit forming the liner  18  with a longitudinal shape other than strictly the straight shape that is currently illustrated; i.e. non-linear configurations. 
         [0027]    The material used for the liner permits the liner  18  to be formed with a variety of bent configurations so that the bushing assembly may also be used to mount the stabilizer bar  10  to the vehicle frame  12  along a bent portion of the bar  10 . One example of a bent bushing and liner is illustrated in  FIG. 4 . The bushing  30  and liner  32  have a bent configuration corresponding to a bend in the stabilizer bar  10 . The bracket  34  securing the bar and bushing assembly to the vehicle frame  12  has a split configuration wherein each leg of the bend of the bushing assembly is individually secured to the vehicle frame  12 . The bracket  34  has a U shaped configuration wherein one side of the U shape is split to create a V shape configuration. The bracket  34  has a pair of securing arms  36 , each arm  36  having two first and second ends  38 ,  40 . At the first end  38  of each securing arm  36  there is a mounting means  42  for attaching the bracket  34  to the frame  12 . The second ends  40  the arms  36  are joined together to form a single mounting area with at least one mounting means  42 . To further secure the location of the bushing  30 , in addition to the ledges at the opposing ends of the bushing  30 , there may be ledges located along the length of the bushing  30  so that each mounting bracket arm  36  is located between a pair of ledges. 
         [0028]    Alternatively, with a bent stabilizer bar  10 , a straight bushing  30  and liner  18  may be located just on one arm of the bend of the bar. Another embodiment for the assembly that may be used with both a straight or bent stabilizer bar is shown in  FIG. 6 . The bushing  16  has a raised central compression area  20  and the ledges  22  at the opposing ends have a reduced height in comparison to the central compression area  20 . The radius of the raised compression area is greater than the radius R M  created by the mounting bracket. 
         [0029]    Suitable, and preferred, materials of construction for the liner  18  include an ultra high molecular weight polyethylene. 
         [0030]    Following manufacture of the bushing  16  and the liner  18 , and even during assembly of the bushing assembly on the stabilizer bar, the liner  18  is maintained as a separate element from the bushing  16 ; i.e. the liner is not bonded or adhesively secured to the bushing. In preparing the bushing assembly, the bushing  16  may be affixed to the liner  18  and then the assembly mounted onto the stabilizer bar  10  or the liner  18  may first be mounted on the stabilizer bar  10  and the bushing  16  is mounted onto the liner. 
         [0031]    By the use of the above described liner and bushing combination, the busing assembly has improved durability due to reduced abrasion between the bushing and the bar and reduced wear of the internal side of the bushing as the bushing no longer rubs against the metal stabilizer bar. Also, friction noise between the bushing and bar is eliminated due to the elimination of contact between the rubber bushing and the metal stabilizer bar.