Abstract:
A suspension top mount is provided with vibration isolating properties by using a rigid insert combined with a stiff elastomer and a soft elastomer to provide tunable combinations of stiffness and damping.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to suspension systems in motor vehicles, and more particularly to a tunable top mount for a suspension system in a motor vehicle.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0002]     Automobile vehicle suspension systems have become highly sophisticated and have proven to be extremely effective in isolating the vehicle from the road vibrations.  
         [0003]     The MacPherson strut-type suspension system is generally used on most subcompact and compact cars with front wheel drive. The MacPherson system features a long telescopic shock absorber strut  10  surrounded by a coil spring  12 . The upper end of the strut is generally isolated by an upper mount  14  that contains a bearing which allows for the turning of the wheel, while the lower end of the strut is typically attached to the steering knuckle  16  of the lower control arm ball joint. The lower control arm can be attached to the underbody side apron of the vehicle, or to the lower side rails of the vehicle, and is also typically attached to the steering knuckle.  
         [0004]     The present invention relates to an improved upper mount for the MacPherson strut system that allows for the top mount to have tunable combinations of stiffness and damping. The top mount of the present invention provides isolation properties while maintaining good ride and handling characteristics. The vibration isolation top mount of the present invention includes a metal insert adapted to be mounted to the suspension strut member. The metal insert has a base portion and a sidewall portion extending from the base portion. An elastomer is disposed on the sidewall portion of the metal insert and a microcellular urethane is disposed on the base portion of the metal insert. The microcellular urethane has less stiffness than the elastomer and allows the stiffness of the top mount to be specifically tuned to absorb vehicular vibrations.  
         [0005]     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  
       [0006]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0007]      FIG. 1  is a plan view of an exemplary MacPherson strut suspension system for a vehicle incorporating the tunable top mount according to the principles of the present invention;  
         [0008]      FIG. 2  is a perspective view of the tunable top mount according to the principles of the present invention;  
         [0009]      FIG. 3  is a cross-sectional view of the tunable top mount according to the principles of the present invention;  
         [0010]      FIG. 4  is a top plan view of the tunable top mount according to the principles of the present invention; and  
         [0011]      FIG. 5  is a cross-sectional view of an alternative embodiment of the tunable top mount according to the principles of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]     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.  
         [0013]     As is described above in the background and summary section, the top mount  14  according to the principles of the present invention is used in a MacPherson strut suspension assembly, but can also be utilized for mounting the top end of any vehicle strut.  
         [0014]     With reference to  FIGS. 2-4 , the tunable top mount  14  includes a rigid metal insert  16 , having a generally cup-shaped configuration with an aperture  18  provided in the base  20  and a cylindrical side wall  22  extending from the base  20 . A microcellular urethane (MCU) is disposed in covering relationship over the exterior surface of the base  20  of the insert  16 . The MCU  24  is generally ring-shaped and provides a cushion between the metal insert  16  and an upper portion of the strut  10 . An elastomer  26  is provided on the exterior surface of the side walls  22  of the insert  16 . The stiff elastomer  26  is stiffer than the MCU  24  and is preferably made from a material such as solid urethane, although other materials such as general families of TPEs, blended elastomers such as SANTOPRENE thermoplastic vulcanizate, SANTOPRENE 8000 thermoplastic vulcanizate, VYRAM thermoplastic vulcanizate, GEOLAST thermoplastic vulcanizate, TREFSIN thermoplastic vulcanizate, VISTAFLEX thermoplastic elastomer, DYTRON thermoelastic elastomer, HYTREL and SARLINK can also be utilized.  
         [0015]     An upper mount plate  28  is provided for mounting the top mount  14  to the vehicle body or frame, as is known in the art. An outer casing or housing  30  surrounds the stiff elastomer  26  and MCU  24 . The metal insert  16 , when surrounded by the elastomer  26  is constrained in the housing  30 . The housing  30  may be made of multiple elements that constrain and in most cases compress the elastomer  26  of the top mount element. The housing  30  can be manufactured independently and can then be bolted, welded or otherwise fastened to the vehicle frame or body. Alternatively, a portion of the housing can be manufactured as an integral part of the vehicle, then the balance of the housing assembly can be assembled or mounted to the vehicle. The aperture  18  in the insert  16  is provided for receiving the upper end of the strut  20  therein for mounting the insert  16  thereto. Top mount  14 , according to the principles of the present invention, allows for tunable combinations of stiffness and damping. The stiffness and thickness of the MCU  24  and the outer layer of elastomer  26  provides the mount with isolation properties that maintain good ride and handling characteristics. A bottom plate  32  (shown in  FIG. 1 ) is connected to the housing  30  and includes a central hole for receiving the strut therethrough. The MCU  24  is contained between the bottom plate  32  and the metal insert  16 . The insert  16  provides a failsafe in case the elastomers are damaged, the insert is sized to prevent the insert from passing through the clearance holes in top of the housing  30  or the bottom plate  32 .  
         [0016]     As illustrated in  FIG. 5 , an alternative top mount arrangement is provided in which the insert  16 ′ is surrounded by the stiff elastomer  26 ′ both along the base  20 ′ and on the interior and exterior of the sidewalls  22 ′. In addition, the MCU  24 ′ is disposed overtop of the stiff elastomer  26 ′ along both the base and sidewalls thereof. Thus, the combination of softer MCU and stiffer elastomeric material can be selectively used to provide appropriate isolation properties. In particular, the base portion “B” of the top mount  14  provides a rebound stopper area while the perimeter portion “P” of the top mount provides a radial sheer area. The top portion “T” of the top mount  14  provides a jounce stopper area.  
         [0017]     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.