Abstract:
An elastomeric isolator has an elastomeric body which incorporates an inner structural member that extends through an outer structural member. The elastomeric body includes an axial shear leg extending between the inner and outer structural members that undergo shearing stresses during deflection of the elastomeric isolator. The inner structural member includes radial flanges which are axially offset from radial flanges of the outer structural member. The axial shear leg extends between the pair of radial flanges and is bonded to them at a position outside of the outer structural member. With this configuration compression of the shear hub during high loads is avoided.

Description:
FIELD 
       [0001]    The present disclosure relates to an isolator such as an automotive exhaust system isolator. More particularly, the present disclosure relates to an isolator which is configured to provide a very soft on-center rate but yet have the ability to endure spike durability loads while avoiding compression and tension of the shear legs of the isolator through their axial orientation. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0003]    Typically, automotive vehicles including cars and trucks have an internal combustion engine which is coupled to at least a transmission and a differential for providing power to the drive wheels of the vehicle. An engine exhaust system which typically includes an exhaust pipe, a catalytic converter and a muffler is attached to the engine to quiet the combustion process, to clean the exhaust gases and to route the products of combustion away from the engine to a desired position typically at the rear of the vehicle. The exhaust system is supported by exhaust mounts which are positioned between the exhaust system and the frame or some other supporting structure of the vehicle body. In order to prevent engine vibrations from being transmitted to the car body, the exhaust mounts incorporate flexible members or elastic suspension members to isolate the vehicle&#39;s exhaust system from the vehicle&#39;s body. In order to effectively isolate the vehicle&#39;s exhaust system from the vehicle&#39;s body, it is preferred that the isolator include a soft on-center rate of deflection. 
         [0004]    The prior art exhaust mounts or isolators have included rubber isolators which are a solid rubber component or a puck that is at least three-quarters of an inch thick and which is provided with at least one pair of apertures extending therethrough. The apertures each receive an elongated metal stud. The metal stud is provided with an enlarged tapered head that can be forced through the aperture in the isolator, but it cannot be readily removed from the isolator. The opposite end of the stud is welded to or otherwise secured to either a support point in the vehicle or to one of the components of the exhaust system. 
         [0005]    Other designs for isolators include elastomeric moldings of a spoke design where spokes are loaded in tension and compression and a shear leg design that include a leg that is subjected to shearing in the primary loading direction. Most elastomers which are utilized for exhaust isolators exhibit poor tensile fatigue properties stemming from low tear strength properties. The preferred method to load the elastomeric material is in compression or shear. 
         [0006]    The prior art puck design is the simplest design, and as discussed above, two pins are inserted at opposite ends of the elastomer and the loads inflict pure tension on the elastomer cords connecting both ends. While this is typically the lowest cost design, it is also the most abusive to the material. In order to offset the failure risk, flexible and/or rigid bands are typically designed inside or around the outside of the elastomeric puck. The advantage of this design is its ability to swivel about one hanger hole to accommodate large positional tolerances for the hanger. 
         [0007]    The prior art spoke design isolators load the elastomeric material in compression and tension. The tensile loading makes the design vulnerable to fractures in overloaded conditions. The stress magnitude is directly proportional to the load divided by the minimum spoke cross-sectional area. An additional requirement of the spoke design is that the mating component or hanger pin be centered within the deflection zone while statically preloaded by the weight of the exhaust system. If it is not, the voids designed into the isolator will be bottomed out or positioned in a groundout condition. This results in the soft on-center rate not being employed, thus defeating the purpose of the isolator. 
         [0008]    The prior art shear leg design has a primary loading direction which is typically vertical and a secondary loading direction which is typically lateral. When the shear leg design is loaded in its primary loading direction, the loading method is the preferred shear style loading. In addition, this shear style loading is able to be designed desirably soft. However, the secondary loading direction inflicts tensile compressive stresses which are unfavorable for durability. In addition, the secondary loading direction has a rate that is two to three times stiffer than the primary rate which is also an unfavorable condition. 
         [0009]    The continued development of elastomeric mounts has been directed to elastomeric mounts which include a soft on-center rate while avoiding the undesirable tension loading of the elastomeric bushing and which avoid the compression of the elastomeric portion of the mount which provides the soft on-center rate during peak loading. 
       SUMMARY 
       [0010]    The present disclosure provides the art with an elastomeric bushing which uses radial loading to avoid the tension stress loading of the bushing. The radial loading cause shear stresses of the elastomeric bushing regardless of the direction of the loading. The portion of the elastomeric bushing which undergoes shear loading is located outside of the reinforcing brackets that resist peak loading. Thus, during peak loading, compression of this portion of the elastomeric bushing is also avoided. 
         [0011]    Further areas of applicability of the present disclosure 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 disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       DRAWINGS 
         [0012]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a perspective view of an elastomeric isolator in accordance with the present disclosure; 
           [0014]      FIG. 2  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 1 ; 
           [0015]      FIG. 3  is a perspective view partially in cross-section illustrating the inner metal of the elastomeric isolator illustrated in  FIG. 1 ; 
           [0016]      FIG. 4A  is a perspective view illustrating the insert for the elastomeric isolator illustrated in  FIG. 1 ; 
           [0017]      FIG. 4B  is a perspective view illustrating an insert for the elastomeric isolator in accordance with another embodiment of the disclosure; 
           [0018]      FIG. 5  is a perspective view of an exhaust system which incorporates the unique exhaust isolators in accordance with the present disclosure; 
           [0019]      FIG. 6  is a perspective view of an elastomeric isolator in accordance with the present disclosure; 
           [0020]      FIG. 7  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 6 ; 
           [0021]      FIG. 8  is a perspective view partially in cross-section illustrating the inner metal of the elastomeric isolator illustrated in  FIG. 6 ; 
           [0022]      FIG. 9  is a perspective view illustrating the insert for the elastomeric isolator illustrated in  FIG. 6 ; 
           [0023]      FIG. 10  is a perspective view of an elastomeric isolator in accordance with the present disclosure; 
           [0024]      FIG. 11  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 10 ; and 
           [0025]      FIG. 12  is a perspective view illustrating the insert for the elastomeric isolator illustrated in  FIG. 10 . 
       
    
    
     DESCRIPTION 
       [0026]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. 
         [0027]    Referring now to the drawings, there is shown in  FIG. 5  an exhaust system which includes the exhaust system isolators in accordance with the present disclosure and which is designated generally by the reference numeral  10 . A typical vehicle comprises an internal combustion engine (not shown), a body (not shown), a suspension system (not shown) and exhaust system  10  which is attached to the internal combustion engine and which is supported typically beneath the vehicle. The internal combustion engine is designed to power one or more drive wheels of the vehicle and the exhaust system routes the products of combustion to a desired exhaust location around the outside of the vehicle. 
         [0028]    Exhaust system  10  comprises an intermediate pipe  12 , a muffler  14 , a tailpipe  16  and a plurality of isolator assemblies of various designs. Intermediate pipe  12  is typically connected to the engine or to a catalytic converter (not shown) which is then attached to an exhaust pipe which extends between the engine and the catalytic converter. The catalytic converter may be attached to a single exhaust pipe which leads to a single exhaust manifold or the catalytic converter can be attached to a branched exhaust pipe which leads to a plurality of exhaust pipes which lead to a plurality of exhaust manifolds. Also, intermediate pipe  12  can be attached to a plurality of catalytic converters which connect together prior to reaching muffler  14  using intermediate pipe  12  or the vehicle can have a plurality of exhaust pipes, a plurality of catalytic converters, a plurality of intermediate pipes  12  and a plurality of mufflers  14  which connect together using a single or multiple tailpipes  16 . In addition, the exhaust system isolator of the present disclosure is applicable to any type of exhaust system including but not limited to dual exhaust systems which have two separate parallel exhaust systems extending from the internal combustion system. 
         [0029]    Exhaust system  10  is utilized to route the exhaust gases from the engine to a desired location around the outside of the vehicle. While traveling through the exhaust system, the catalytic converter cleans the exhaust gases and muffler  14  quiets the noise created during the combustion process in the engine. The present disclosure is directed toward the exhaust system isolators which mount exhaust system  10  to the vehicle while at the same time, isolate the movement of exhaust system  10  with respect to the vehicle. 
         [0030]    Referring now to  FIGS. 1-4B , an exhaust system isolator  30  is disclosed. Exhaust system isolator  30  comprises an inner structural member  32 , an outer structural member  34  and an elastomeric body  36 . 
         [0031]    Elastomeric body  36  defines a first bore  40  and a second bore  42 , each of which is designed as a structural member to accept an inner tube, a bolt or a hanger pin  44 . One hanger pin  44  is attached to a structural component of the vehicle and one hanger pin  44  is attached to a component of exhaust system  10 . 
         [0032]    Elastomeric body  36  defines a circumferential void  46  which is located below first bore  40  and which extends through elastomeric body  36 . The portion of elastomeric body  36  that forms second bore  42  defines circumferential void  46 . The design of circumferential void  46  and the design of the portion of elastomeric body  36  that forms second bore  42  will determine the amount of travel of second bore  42  with respect to first bore  40  until the load to radially deflect exhaust system isolator  30  spikes up due to the closing of circumferential void  46  or the gap between the portion of elastomeric body  36  that defines second bore  42  and the portion of elastomeric body  36  that encases outer structural member  34 . Until circumferential void  46  or this gap is closed, radial movements of second bore  42  with respect to first bore  40  cause pure shear in elastomeric body  36  regardless of the loading direction. This shear loading occurs in a pair of axial shear legs  50  defined by elastomeric body  36  which are disposed between outer structural member  34  and inner structural member  32  as discussed below. Tuning for rate and deflection in selected directions can be accomplished independently from other directions by altering the design of elastomeric body  36  using different shaped voids, additional voids, different shapes for elastomeric body  36  and by other means known well in the art. 
         [0033]    As can be seen from the figures, the portion of elastomeric body  36  which forms second bore  42  is attached to the portion of elastomeric body  36  which forms first bore  40  and circumferential void  46  by the pair of axial shear legs  50 . During movements of exhaust system isolator  30 , axial shear legs  50  are loaded in shear. During larger movements of exhaust system isolator  30 , the gap between the portion of elastomeric body  36  forming second bore  42  and the portion of elastomeric body  36  forming circumferential void  46  closes. At this point in time, the rate of deflection of exhaust system isolator  30  spikes up because the load is now being resisted by inner structural member  32  and outer structural member  34  rather than by axial shear legs  50 . One of the advantages for exhaust system isolator  30  is that when this gap is closed, there is no direct tension or compression of axial shear legs  50 . 
         [0034]    Inner structural member  32  is a metal or plastic component which comprises a generally cylindrical center portion  52  and a flange portion  54  attached to one end of generally cylindrical center portion  52 . Generally cylindrical center portion  52  extends over second bore  42  and flange portion  54  extends radially outward from diametrically opposite sides of generally cylindrical center portion  52 . Each side of flange portion  54  provides a base for a respective axial shear leg  50 . Elastomeric body  36  encapsulates inner structural member  32  and is bonded to inner structural member  32  including axial shear legs  50  being bonded to flange portion  54 . 
         [0035]    Outer structural member  34  is a metal or plastic component which comprises an annular main portion  60  having a pair of flanges  62  extending radially outward from opposite sides of main portion  60  and a partition wall  64  which divides the center of main portion  60  into an upper cylindrical portion  66  and a central aperture  68 . As illustrated in  FIG. 4A , partition wall  64  comprises two walls  70  and  72  which meet at their center points. As illustrated in  FIG. 4B , partition wall  64  comprises a single wall  74 . Upper cylindrical portion  66  of main portion  60  surrounds first bore  40  to provide support for holding hanger pin  44 . Central aperture  68  of main portion  60  defines circumferential void  46  and the portion of main portion  60  that forms central aperture  68  provides support for contact between inner structural member  32  and outer structural member  34 . Each flange  62  is disposed opposite to a respective side of flange portion  54  to provide a base for a respective axial shear leg  50 . Elastomeric body  36  encapsulates outer structural member  34  and is bonded to outer structural member  34  including axial shear legs  50  being bonded to flanges  62 . 
         [0036]    Axial shear legs  50  are arranged in an axial direction of exhaust system isolator  30  such that any radial loading from the application causes shear stress in axial shear legs  50 . In addition, axial shear legs  50  are not disposed between portions of inner structural member  32  and outer structural member  34  which will contact each other during peak loading. Thus, during peak loadings, axial shear legs  50  are not compressed between inner structural member  32  and outer structural member  34 . 
         [0037]    Referring now to  FIGS. 6-9 , an exhaust system isolator  130  is disclosed. Exhaust system isolator  130  comprises an inner structural member  132 , an outer structural member  134  and an elastomeric body  136 . 
         [0038]    Elastomeric body  136  defines a first bore  140  and a second bore  142 , each of which is designed as a structural member to accept an inner tube, a bolt or a hanger pin  44 . One hanger pin  44  is attached to a structural component of the vehicle and one hanger pin  44  is attached to a component of exhaust system  10 . 
         [0039]    Elastomeric body  136  defines a circumferential void  146  which is located below first bore  140  and which extends through elastomeric body  136 . The portion of elastomeric body  136  that forms second bore  142  defines circumferential void  146 . The design of circumferential void  146  and the design of the portion of elastomeric body  136  that forms second bore  142  will determine the amount of travel of second bore  142  with respect to first bore  140  until the load to radially deflect exhaust system isolator  130  spikes up due to the closing of circumferential void  146  or the gap between the portion of elastomeric body  136  that defines second bore  142  and the portion of elastomeric body  136  that encases outer structural member  134 . Until circumferential void  146  or this gap is closed, radial movements of second bore  142  with respect to first bore  140  cause pure shear in elastomeric body  136  regardless of the loading direction. This shear loading occurs in a pair of axial shear legs  150  defined by elastomeric body  136  which are disposed between outer structural member  134  and inner structural member  132  as discussed below. Tuning for rate and deflection in selected directions can be accomplished independently from other directions by altering the design of elastomeric body  136  using different shaped voids, additional voids, different shapes for elastomeric body  136  and by other means known well in the art. 
         [0040]    As can be seen from the figures, the portion of elastomeric body  136  which forms second bore  142  is attached to the portion of elastomeric body  136  which forms first bore  140  and circumferential void  146  by the pair of axial shear legs  150 . During movements of exhaust system isolator  130 , axial shear legs  150  are loaded in shear. During larger movements of exhaust system isolator  130 , the gap between the portion of elastomeric body  136  forming second bore  142  and the portion of elastomeric body  136  forming circumferential void  146  closes. At this point in time, the rate of deflection of exhaust system isolator  130  spikes up because the load is now being resisted by inner structural member  132  and outer structural member  134  rather than axial shear legs  150 . One of the advantages for exhaust system isolator  130  is that when this gap is closed, there is no direct tension or compression of axial shear legs  150 . 
         [0041]    Inner structural member  132  is a metal or plastic component which comprises a generally cylindrical center portion  152  and a flange portion  154  attached to one end of generally cylindrical center portion  152 . Generally cylindrical center portion  152  extends over second bore  142  and flange portion  154  extends radially outward from diametrically opposite sides of generally cylindrical center portion  152 . Each side of flange portion  154  provides a base for a respective axial shear leg  150 . Elastomeric body  136  encapsulates inner structural member  132  and is bonded to inner structural member  132  including axial shear leg  150  being bonded to flange portion  154 . 
         [0042]    Outer structural member  134  is a metal or plastic component which comprises a main portion  160  having a pair of generally planar walls or flanges  162  which define and radially extend out from a central aperture  164 , an axially extending cylindrical section  166  which surrounds first bore  140  to provide support for holding hanger pin  44 , a pair of axially extending stops  168  which limit the travel of inner structural member  132  with respect to outer structural member  134  and a partition wall  170  disposed between axially extending cylindrical section  166  and central aperture  164 . Each planar wall or flange  162  is disposed opposite to a respective side of flange portion  154  to provide a base for a respective axial shear leg  150 . Elastomeric body  136  encapsulates outer structural member  134  and is bonded to outer structural member  134  including axial shear legs  150  being bonded to generally planar walls or flanges  162 . 
         [0043]    Axial shear legs  150  are arranged in an axial direction of exhaust system isolator  130  such that any radial loading from the application causes shear stress in axial shear legs  150 . In addition, axial shear legs  150  are not disposed between portions of inner structural member  132  and outer structural member  134  which will contact each other during peak loading. Thus, during peak loadings, axial shear legs are not compressed between inner structural member  132  and outer structural member  134 . 
         [0044]    Referring now to  FIGS. 10-12 , an exhaust system isolator  230  is disclosed. Exhaust system isolator  230  comprises an inner structural member  232 , an outer structural member  234  and an elastomeric body  236 . 
         [0045]    Elastomeric body  236  defines a bore  240  which is designed as a structural member to accept an inner tube, a bolt or a hanger pin  44 . Hanger pin  44  is attached to either a structural component of the vehicle or hanger pin  44  is attached to a component of exhaust system  10 . 
         [0046]    Elastomeric body  236  defines a circumferential void  246  which is located around bore  240  and which extends through elastomeric body  236 . The design of circumferential void  246  will determine the amount of travel of bore  240  until the load to radially deflect exhaust system isolator  230  spikes up due to the closing of circumferential void  246 . Until circumferential void  246  or this gap is closed, radial movements of bore  240  cause pure shear in elastomeric body  236  regardless of the loading direction. This shear loading occurs in a pair of axial shear legs  250  defined by elastomeric body  236  which are disposed between outer structural member  234  and inner structural member  232  as discussed below. Tuning for rate and deflection in selected directions can be accomplished independently from other directions by altering the design of elastomeric body  236  using different shaped voids, additional voids, different shapes for elastomeric body  236  and by other means known well in the art. 
         [0047]    As can be seen from the figures, the portion of elastomeric body  236  which defines the outer wall of void  246  is attached to the portion of elastomeric body  236  which forms bore  240  by the pair of axial shear legs  250 . During movements of exhaust system isolator  230 , axial shear legs  250  are loaded in shear. During larger movements of exhaust system isolator  230 , the gap between the portion of elastomeric body  236  forming the outer wall defining void  246  and the portion of elastomeric body  236  forming bore  240  closes. At this point in time, the rate of deflection of exhaust system isolator  230  spikes up because the load is now being resisted by inner structural member  232  and outer structural member  234  rather than axial shear legs  250 . One of the advantages for exhaust system isolator  230  is that when this gap is closed, there is no direct tension or compression of axial shear legs  250 . 
         [0048]    Inner structural member  232  is a metal or plastic component which comprises a generally cylindrical center portion  252  and a flange portion  254  attached to one end of generally cylindrical center portion  252 . Generally cylindrical center portion  252  extends over bore  240  and flange portion  254  extends radially outward from diametrically opposite sides of generally cylindrical center portion  252 . Each side of flange portion  254  provides a base for a respective axial shear leg  250 . Elastomeric body  236  encapsulates inner structural member  232  and is bonded to inner structural member  232  including axial shear leg  250  being bonded to flange portion  254 . 
         [0049]    Outer structural member  234  is a metal or plastic component which comprises a main portion  260  having a pair of generally planar walls or flanges  262  which define and radially extend out from a central aperture  264 , an axially extending cylindrical section  266  which surrounds bore  240  to provide a stop for bore  240  and an axially extending planar wall  268  which extends generally perpendicular to main portion  260  and includes a mounting stud  270  extending generally perpendicular to planar wall  268 . While planar wall  268  is disclosed as being generally perpendicular to main portion  260 , it is within the scope of the present disclosure to have planar wall  268  extend at any angle with respect to main portion  260 . Also, while mounting stud  270  is disclosed as a threaded mounting stud, it is within the scope of the present disclosure to design mounting stud  270  such that any other fastening means known in the art can be combined or mated with mounting stud  270 . Each planar wall or flange  262  is disposed opposite to a respective side of flange portion  254  to provide a base for a respective axial shear leg  250 . Elastomeric body  236  encapsulates outer structural member  234  and is bonded to outer structural member  234  including axial shear legs  250  being bonded to generally planar walls or flanges  262 . 
         [0050]    Axial shear legs  250  are arranged in an axial direction of exhaust system isolator  230  such that any radial loading from the application causes shear stress in axial shear legs  250 . In addition, axial shear legs  250  are not disposed between portions of inner structural member  232  and outer structural member  234  which will contact each other during peak loading. Thus, during peak loadings, axial shear legs are not compressed between inner structural member  232  and outer structural member  234 . 
         [0051]    The mounting system for exhaust system isolator  30  exhaust system isolator  130  or exhaust system isolator  230  is not limited to hanger pins  44  illustrated above or hanger pins and a stud as illustrated above. Any of the mounting systems disclosed in Applicant&#39;s co-pending application Ser. No. 11/233,283, the disclosure of which is incorporated herein by reference, could be used to mount exhaust system isolator  30 ,  130  or  230  to the vehicle by changing main portion  60 ,  160  or  260  of exhaust system isolator  30 ,  130  or  230  to the mounting systems disclosed in the co-pending application.