Patent Publication Number: US-2006012090-A1

Title: Multi-direction tuned mass damper with unique assembly

Description:
FIELD OF THE INVENTION  
      The present invention relates to a mass damper for an automotive suspension. More particularly, the present invention relates to a multi-directional mass damper which is assembled to a component of an automotive suspension.  
     BACKGROUND OF THE INVENTION  
      As a type of vibration damping device for reducing vibrations of a rod-shaped member, such as a shaft, a torque rod or a suspension link, used in various suspension components, there is known a mass damper having a single direction of tuned functionality. The single direction limitations of the prior art damping devices is due to their construction. Typically these prior art mass dampers consist of a rubber pad having a mass chemically bonded to one side of the rubber pad. A mounting bracket chemically bonded to the other side of the rubber pad is utilized to mount or attach the mass damper to the vibrating component. The design for the rubber pad and the mass are chosen to have a natural frequency that corresponds to the natural frequency that needs to be damped.  
      One problem with the prior art mass dampers is that they are limited to providing improved damping in only a single direction. When a specific application requires that vibration damping is required in multiple directions, the only option is to provide a separate single direction mass damper for each direction that requires damping.  
     SUMMARY OF THE INVENTION  
      The present invention provides the art with a multi-directional damper which effectively dampens vibrations in multiple directions. The design for the multi-directional damper also provides for a unique and uncomplicated method for assembly, saving both time and money.  
      Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
       FIG. 1  is a side view of a link assembly incorporating a mass damper in accordance with the present invention;  
       FIG. 2  is a plan view of the link assembly illustrated in  FIG. 1 ;  
       FIG. 3  is an end view of one of the mass dampers illustrated in  FIGS. 1 and 2 ;  
       FIG. 4  is a side cross-sectional view of the mass damper illustrated in  FIG. 3 ;  
       FIG. 5  is an end view similar to  FIG. 3  but illustrating a mass damper in accordance with another embodiment of the invention;  
       FIG. 6  is an end view of the other mass damper illustrated in  FIGS. 1 and 2 ; and  
       FIG. 7  is a side cross-sectional view of the mass damper illustrated in  FIG. 5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
      There is illustrated in  FIGS. 1 and 2  a link assembly  10  which incorporates mass dampers in accordance with the present invention. Link assembly  10  comprises a pair of fittings in the form of elastomeric bushing assemblies  12 , a solid or tubular center rod  14 , a mass damper assembly  16  and a mass damper assembly  18 .  
      Each elastomeric bushing assembly  12  comprises an eyelet  22 , a center connection fitting  24  and an elastomeric bushing  26  disposed between eyelet  22  and center connection fitting  24 . Each elastomeric bushing assembly  12  is attached to an end of center rod  14  by welding or by other means known in the art. Link assembly  10  is connected between two components of a suspension system utilizing the appropriate connectors and center connection fittings  24 .  
      Referring now to  FIGS. 3 and 4 , mass damper assembly  16  is illustrated in greater detail. Mass damper assembly  16  comprises an outer annular mass  32  and an inner elastomeric bushing  34 . The design for elastomeric bushing  34  is chosen to damp a single specific frequency and it may include one or more annular cut outs  36  to tune it to the correct frequency. Elastomeric bushing  34  is mechanically or chemically bonded to annular mass  32  and the size and design for mass  32  is also chosen based upon the natural frequency to be damped. While annular mass  32  is illustrated as having a constant wall thickness, it is within the scope of the present invention to vary the wall thickness of the annular mass to have different frequency responses in specific radial directions as illustrated in  FIG. 5 .  
       FIG. 5  illustrates a mass damper assembly  16 ′ which comprises outer mass  32 ′ and inner elastomeric bushing  34 . Elastomeric bushing  34  is mechanically or chemically bonded to outer mass  32 ′ similar to that described above for mass damper assembly  16 . Mass damper assembly  16 ′ is the same as mass damper assembly  16  described above except for the replacement of outer mass  32  with outer mass  32 ′. Outer mass  32 ′ is a multiple piece mass where the individual pieces are different sizes and thus different masses. Outer mass  32 ′ has a first natural frequency in one radial direction and a different second natural frequency in a second radial direction which will dampen different frequencies in the different radial directions due to the variable sized multi-piece construction of outer mass  32 ′. While outer mass  32 ′ is illustrated as a multiple piece mass, it is within the scope of the present invention to utilize a single piece mass  16 ′ which includes the different wall thickness or masses arranged circumferentially around elastomeric bushing  34 .  
      The assembly of mass damper assembly  16  or  16 ′ is accomplished by stretching the inner diameter of elastomeric bushing  34  and sliding the pre-assembled mass damper assembly  16  or  16 ′ onto center rod  14  prior to the welding of one or both of eyelets  22  of elastomeric bushing assemblies  12 . Once positioned at the proper axial and circumferential position on center rod  14 , mass damper assembly  16  or  16 ′ is held in position by mechanically or chemically bonding elastomeric bushing  34  to center rod  14 . The bonding of elastomeric bushing  34  to center rod  14  removes the need for fasteners and/or bolted joints to attach the mass damper to the suspension link. Once the mass dampers have been bonded to center rod  14 , the assembly continues with the welding of the remaining eyelets  22  and the assembly of elastomeric bushing assemblies  12 .  
      Mass damper assembly  16  or  16 ′ is capable of damping vibrations in multiple radial directions and thus eliminates the need for having a separate tuned damper for each direction that requires additional damping.  
      Referring now to  FIGS. 6 and 7 , mass damper assembly  18  is illustrated in greater detail. Mass damper assembly  18  comprises outer annular mass  32  and an inner elastomeric bushing  134 . Elastomeric bushing  134  is the same as elastomeric bushing  34  except that elastomeric bushing  134  includes one or more voids  136  to provide different frequency responses in specific radial directions. The design for elastomeric bushing  134  is chosen to have a first natural frequency in a first radial direction and a different second natural frequency in a second radial direction to dampen a first specific frequency in the first specific radial direction due to the incorporation of voids  136  and a second specific frequency in the second radial direction due to the elimination of voids  136 . Elastomeric bushing  134  is mechanically or chemically bonded to annular mass  32 . While mass damper assembly  18  is illustrated incorporating annular mass  32 , it is within the scope of the present invention to incorporate annular mass  32 ′ in place of annular mass  32 . This design is illustrated in  FIG. 5  where voids  136  have been shown in phantom.  
      The assembly of mass damper assembly  18  is the same as that described above for mass damper assembly  16  and once assembled, mass damper assembly  18  is held in position by mechanically or chemically bonding elastomeric bushing  134  to center rod  14 .  
      The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.