Abstract:
A stabilizer bar assembly has a stabilizer bar and a pair of bushing assemblies. Each bushing assembly has an elastomeric bushing disposed around the stabilizer bar and an outer metal member disposed around the elastomeric bushing. The outer metal member compresses the elastomeric bushing between the stabilizer bar and the outer metal member to a prespecified percent of compression. When the stabilizer bar rotates with respect to the outer metal member, the compression of the elastomeric bushing stops movement between the elastomeric bushing and the stabilizer bar and between the elastomeric bushing and the outer metal member. A fastening strap is attached to the outer metal member to attach the stabilizer bar assembly to a vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 09/408,406 filed Sep. 9, 1999. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to stabilizer bar bushings. More particularly, the present invention relates to a stabilizer bar bushing which incorporates anti-slip features to eliminate slip between the bushing and the stabilizer bar.  
         BACKGROUND OF THE INVENTION  
         [0003]    Conventional motor vehicle suspension systems often include one or more stabilizer bars to control the degree of roll of the motor vehicle during cornering or other vehicle maneuvers. A typical stabilizer bar is generally U-shaped having a long intermediate portion disposed laterally with respect to the motor vehicle and a pair of relatively short end portions extending forwardly or rearwardly to connect to a corresponding pair of suspension arms or wheel hubs. The intermediate portion normally is connected to the underside of the vehicle by one or more bracket assemblies.  
           [0004]    The mounting bracket assembly for the intermediate portion of the stabilizer bar typically includes an elastomeric bushing, sometimes termed an insulator, and a bracket which is secured to the underside of the vehicle. The elastomeric bushing is located between the stabilizer bar and the bracket to support and isolate the stabilizer bar. In some applications it is desirable to use an elastomeric bushing that permits the stabilizer bar to rotate freely about the axis of the intermediate portion of the stabilizer bar. In other applications, it is desirable to allow partial wind-up of the bushing and then allowing the bushing to slip for relative torsional travel between the bushing and the bar. In still other applications, attempts are made to eliminate the slippage of the bushing such that all rotation of the stabilizer bar is resisted by wind-up of the bushing.  
           [0005]    The designs that allow rotation between the bar and the bushing have attempted to minimize friction at the bushing/stabilizer bar interface by employing low-friction materials as liners covering the bore of the bushing or by adding lubricants between the bushing and the stabilizer bar. Commonly used materials for bushing liners are polyester or polytetra fluoroethylene while silicone greases have been utilized as lubricants. The primary disadvantage of these designs is that the liner wears or the lubricant dissipates resulting in an unacceptable audible squawk in the vehicle. Also, with these designs, environmental contamination can result in premature wear of the liner or premature dissipation of the lubricant thus leading to the audible squawk.  
           [0006]    The designs that allow partial wind-up and then allow slippage of the stabilizer bar with respect to the bushing suffer from the same disadvantages as the designs that allow total rotation in that early wear and/or contamination of the interface between the bar and the bushing can lead to an audible squawk.  
           [0007]    The designs that attempt to eliminate all slippage of the bushing have been successful for limited rotation of the stabilizer bar with respect to the bushing, but larger rotation of the stabilizer bar has caused deterioration of the bushing and/or slippage of the bushing. In order to overcome these problems, some prior art designs have incorporated flats on the stabilizer bar or other components which resist rotation of the bushing. While the incorporation of flats has resisted the larger amounts of rotation, the costs and complexities of these designs have limited their applicability.  
           [0008]    The continued development of stabilizer bar bushings and attachment systems has been directed toward designs which provide additional durability, eliminate the audible squawking by eliminating the rotation between the stabilizer bar and the bushing but yet still perform the required isolation between the stabilizer bar and the vehicle.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention provides the art with an attachment between the stabilizer bar and the supporting structure of the vehicle which will improve the durability of the bushing, provide isolation for the stabilizer bar and allow for the proper positioning of the stabilizer bar relative to the frame. The present invention provides for radial, axial, torsional and conical loading of the stabilizer bar due to jounce and rebound of the suspension. The present invention provides this relative movement between the stabilizer bar and the frame without slippage between the bushing and the stabilizer bar thus eliminating the potential for an audible squawk.  
           [0010]    The present invention utilizes a mechanically bonded bushing assembled over the stabilizer bar and then compressed into an outer sleeve/bracket assembly. The bracket assembly is provided with slotted holes to compensate for the stabilizer bar assembly and the vehicle body tolerance stack-ups. This preassembly of the bushings and the stabilizer bar also allows the assembly to be supplied directly to the assembly plants ready for vehicle assembly. This is opposed to the prior art which supplies the stabilizer bar and the bushings as separate components requiring sub-assembly at the vehicle assembly plant. The stabilizer bar attachment of the present invention provides both axial and lateral location proximate to the vehicle body and suspension attachments, the torsional resistance of the elastomeric member provides enhanced anti-roll capabilities, and due to the lack of slippage between the elastomeric member and the bore, a noise free pivot attachment with enhanced longevity and product life is provided.  
           [0011]    Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    In the drawings which illustrate the best mode presently contemplated for carrying out the present invention:  
         [0013]    [0013]FIG. 1 is a plan view of a stabilizer bar assembly incorporating the unique bushing assembly in accordance with the present invention;  
         [0014]    [0014]FIG. 2 is an enlarged view of the bushing assembly in accordance with the present invention;  
         [0015]    [0015]FIG. 3 is an end view of the bushing assembly shown in FIG. 2;  
         [0016]    [0016]FIG. 4 is a cross-sectional view of the elastomeric bushing for the bushing assembly of the present invention;  
         [0017]    [0017]FIG. 5 is a cross-sectional view of the outer tube for the bushing assembly of the present invention;  
         [0018]    [0018]FIG. 6 is a cross-sectional view of the strap for the bushing assembly of the present invention; and  
         [0019]    [0019]FIG. 7 is an end view of a typical strap and outer metal member for the assembly of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a stabilizer bar assembly which is identified generally by the reference numeral  10 . Stabilizer bar assembly  10  comprises a stabilizer bar  12  and a pair of bushing assemblies  14 . Stabilizer bar  12  is a generally U-shaped bar having a center sectional  16  and a pair of end sections  18  and  20 . Center section  16  is designed to be secured to the sprung mass of the vehicle by bushing assemblies  14 . End sections  18  and  20  are designed to be secured to the left and right suspension control arms or hubs (not shown) of the vehicle to which stabilizer bar assembly  10  is designed for. The various bends and unique configurations for stabilizer bar  12  permit stabilizer bar assembly  10  to function in the particular vehicle without interfering with the components of the vehicle which are positioned within the general area of stabilizer bar assembly  10 .  
         [0021]    Referring now to FIGS.  2 - 7 , bushing assembly  14  comprises an elastomeric bushing  40 , an outer metal member  42  and a fastening strap  44 . As shown in FIG. 4, elastomeric bushing  40  is an annular member which includes an inside diameter  46  having a specified dimension and an outside diameter  48  having a specified dimension. Inside diameter  46  is designed to be smaller than the bar diameter for stabilizer bar  12 . Outside diameter  48  is designed to be larger than an inside diameter  50  of outer metal member  42  when elastomeric bushing  40  is assembled over stabilizer bar  12 . This dimensioning provides a specified amount of compression for elastomeric bushing  40  to provide the mechanical friction between elastomeric bushing  40  and stabilizer bar  12  and between elastomeric bushing  40  and outer metal member  42 . This mechanical friction allows for torsional wind-up and deflection of elastomeric bushing  40  to prevent any slippage between the mating components.  
         [0022]    In the preferred embodiment, the percent compression for elastomeric bushing  40  after it is assembled over stabilizer bar  12  and within outer metal member  42  is between 20% to 60% compression and more preferably it is between 35% and 50%. When the percent of compression for elastomeric bushing  40  is less than 20%, slippage of elastomeric bushing  40  can occur. When the percent of compression for elastomeric bushing exceeds approximately 60%, the assembly of elastomeric bushing  40  and stabilizer bar  12  within outer metal member  42  becomes difficult and/or impractical.  
         [0023]    Outer metal member  42  is a tubular member having a cylindrical body  52  defining inside diameter  50  and an optional flanged end  54  shown in phantom in the figures. While outer metal member  42  is illustrated in phantom as being provided with flanged end  54 , it is within the scope of the present invention to provide outer metal member  42  with a non-flanged end. Flanged end  54  can be utilized to aid in the assembly of bushing assembly  14  onto stabilizer bar  12  if desired. In the preferred embodiment, outer metal member  42  is provided without flange  54  making outer metal member  42  a cylindrical tube. Fastening strap  44  comprises a C-shaped body  60  and a pair of flanges  62 . C-shaped body  60  is sized to mate with the outside diameter of outer metal member  42  and as shown in FIG. 7. Fastening strap  44  is secured to outer metal member  42  by welding or other methods known in the art. Each flange  62  extends outward from body  60  and defines a slotted hole  64  which is used to secure stabilizer bar assembly  10  to the sprung mass of the vehicle. The slotting of holes  64  compensate for the various tolerance stack-ups which occur in the vehicle itself as well as the tolerances in stabilizer bar assembly  10 . Each flange  62  may include a pair of gussets  66  which can provide support for securing stabilizer bar assembly  10  to the vehicle.  
         [0024]    Once bushing assemblies  14  are assembled to stabilizer bar  12 , stabilizer bar assembly  10  is ready to be assembled directly into the vehicle. This eliminates the prior art system of providing a separate stabilizer bar and bushings which require subassembly at the vehicle manufacturing plant prior to be assembled into the vehicle. Attempting to ship the prior art stabilizer bars as a complete assembly has resulted in the misplacement or loss of the bushings because of the lack of retention of the bushings to the stabilizer bar prior to being installed into the vehicle.  
         [0025]    The assembly of bushing assemblies  14  onto stabilizer bar  12  places a pre-specified percent compression of elastomeric bushing  40 . In the preferred embodiment, the percent compression of elastomeric bushing  40  is between 20% and 60% and more preferably it is between 35% and 50%. Due to the relatively high percent compression of elastomeric bushing  40 , the slipping between elastomeric bushing  40  and stabilizer bar  12  and between elastomeric bushing and outer metal member  42  is eliminated for specific suspension travel requirements. Any pivoting or rotation of the stabilizer bar  12  during vehicle operation with respect to bushing assembly  14  causes wind-up or deflection of elastomeric bushing  40  without slipping between the components. Because the slipping between the components is eliminated, the potential for creating an audible squawk is eliminated. Due to the relatively high percent compression for elastomeric bushing  40 , stabilizer bar  12  can rotate up to as much as 60° in either direction without slippage of elastomeric bushing  40 . During suspension movement within a vehicle, the full jounce and full rebound positions of the suspension require that stabilizer bar  12  rotate less than this 60° allowable by bushing assembly  14  thus eliminating slippage of elastomeric bushing  40 . In addition to eliminating slippage of elastomeric bushing  40 , the high percent compression for elastomeric bushing  40  also improves steering response for the vehicle, it increases roll stiffness to improve vehicle handling, it enhances on-center steering response and on-center steadiness, it provides better high-speed lane-change stability, it improves overall vehicle handling and lateral stability, it enhances durability and it isolates stabilizer bar  12  and allows for the proper positioning of stabilizer bar  12  relative to the vehicle frame.  
         [0026]    Another advantage of the high percent compression of elastomeric bushing  40  of bushing assembly  14  is the increase in the lateral/axial restraint of stabilizer bar  12  and the increase in the bending resistance for stabilizer bar  12 . The increase in the lateral/axial restraint of stabilizer bar  12  causes stabilizer bar  12  to remain axially or laterally positioned during vehicle maneuvers. By maintaining the proper axial/lateral position, stabilizer bar  12  improves the vehicle handling characteristics. The increase in the bending resistance for stabilizer bar  12  provided by bushing assemblies  14  increases the pure torsional or rotational movement of stabilizer bar  12  with respect to bushing assemblies  14 . This improves vehicle handling due to the fact that the pivot points or the axis of rotation for stabilizer bar  12  remain more nearly fixed in the radial loaded direction.  
         [0027]    Stabilizer bar assembly  10  is manufactured in a unique manner for stabilizer bar assemblies. Once stabilizer bar  12  has been manufactured with the proper configuration, two elastomeric bushings  40  are located on stabilizer bar  12  at the proper location. Because inside diameter  46  is smaller than the bar diameter for stabilizer bar  12 , the interference fit between bushings  14  and stabilizer bar  12  maintain the proper positioning for bushings  14 . A respective outer metal member  42  is assembled over each elastomeric bushing  40  by compressing each elastomeric bushing  40  to a specified percent compression and then inserting each elastomeric bushing  40  within the respective outer metal member  42  to produce bushing assemblies  14 . In the preferred embodiment, the percent compression for each elastomeric bushing  40  is between 20% and 60% and more preferably between 35% and 50%. Bushing assemblies  14  can be assembled separately or one at a time or bushing assemblies  14  can be simultaneously assembled. Once assembled, the highly compressed bushing assemblies  14  provide the advantages detailed above.  
         [0028]    While the above detailed description describes the preferred embodiment of the present invention, it should be understood that the present invention is susceptible to modification, variation and alteration without deviating from the scope and fair meaning of the subjoined claims.