Abstract:
A body mount for use in motor vehicles in which the mount is sandwiched between the subframe and body. The mount has an insert member with an oblong shape in the lateral displacement direction of the vehicle. The insert member is surrounded by a microcellular urethane body. The oblong shape increases the compression of the microcellular urethane body that can be used to respond to lateral forces. The lateral response rate can be stiffer than the fore and aft response rate. The isolation mount also can facilitate fine tuning thereof by selectively indenting a cup member surrounding the microcellular urethane body to adjust the vibration characteristics of the body mount.

Description:
FIELD 
     The present disclosure relates to an isolation mount used in securing a support structure to a vehicle body, such as a vehicle cradle mount or subframe, and for absorbing vibrations and movements between the two structures. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Subframe mounts are used extensively in unibody vehicles to isolate vibrations created by road inputs from being transmitted from the engine to the subframe and the body, and vice versa. The operator of the vehicle perceives that vibration isolation relates to ride quality and that improved vehicle dynamics translates into improved handling performance. 
     Typically, there are as many as four locations on the sub-frame where an isolation mount is utilized. The sub-frame is compressed between the upper portion and the lower portion of the vibration mount and the vehicle body rests on top of the upper mount. A bolt extends through an aperture in the sub-frame and the isolation mount. The lower mount and the upper mount are connected by a weld nut on the body to complete the attachment, of the body to the sub-frame. The mount isolates road inputs and engine or transmission induced vibration that is transmitted along the sub-frame to the body. The mount also improves vehicle dynamics by controlling or attenuating relative movement between the vehicle body and sub-frame in the vertical mode or plane, that is up and down, relative movement, and also to control lateral mode or plane, that is side to side movement, and fore and aft mode or plane, that is front to back relative movement. 
     A typical design of a sub-frame isolation mount employs a relatively hard or high durometer rubber (typically 40 to 80 Shore A) as an isolating material. High durometer rubber for cradle or sub-frame mounts is an excellent material for improved handling in the lateral plane, especially when it is combined with rate plates to stiffen the response in the lateral plane and to a limited degree the fore and aft plane. However, since the solid elastomeric material is generally very stiff, it does not attenuate vertical forces from the subframe to the body very effectively. As a result, the isolation mount has a high lateral stiffness rate response which is desirable but it has a fore aft stiffness rate response which is marginally acceptable and a vertical stiffness rate response which is low. Therefore, good ride and handling of a vehicle are compromised because of the stiffness properties of the solid elastomeric material. 
     Thus, there is a need for a vibration isolation mount that provides for ride quality that is satisfactory to the operator without sacrificing the handling characteristics of the vehicle in the lateral plane, fore and aft plane and vertical plane. Additionally, there is a need for a mount that is lighter in weight, improves durability and reduces both initial and high mileage noise, vibration, and harshness between a sub-frame and a body. 
     SUMMARY 
     Accordingly, the present disclosure provides a mount assembly for mounting a support structure to a vehicle body, such as a frame, sub-frame or vehicle cradle mount. The mount assembly includes an insert including a generally cylindrical body having an aperture extending therethrough and a first pair of radial projections and a second pair of radial projections. The first pair of radial projections extend at a distance greater than the second pair of radial projections. A microcellular urethane body is press-fit over the insert in order to pre-compress the body. A cup member surrounds a portion of the microcellular urethane body. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a cross-sectional view of the body mount assembly according to the principles of the present disclosure; 
         FIG. 2  is a perspective view of an insert for use with the body mount assembly according to the principles of the present disclosure; 
         FIG. 3  is a top plan view of the insert of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of the insert taken along line  4 - 4  of  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of the insert taken along line  5 - 5  of  FIG. 3 ; 
         FIG. 6  is a bottom plan view of a micro-cellular urethane body and cup assembly for use with the mount of  FIG. 1 ; 
         FIG. 7  is a cross-sectional view taken along line  7 - 7  of  FIG. 6 ; 
         FIG. 8  is a perspective view of the cup utilized with the mount assembly shown in  FIG. 1 ; 
         FIG. 9  is a cross-sectional view of the cup of  FIG. 8 ; 
         FIG. 10  is a cross-sectional view of a body mount assembly according to a second embodiment of the present disclosure; 
         FIG. 11  is a perspective view of an insert utilized with the body mount assembly shown in  FIG. 10 ; 
         FIG. 12  is a top plan view of the insert of  FIG. 11 ; 
         FIG. 13  is a cross-sectional view taken along line  13 - 13  of  FIG. 12 ; 
         FIG. 14  is a bottom view of a micro-cellular urethane body and cup assembly for use with the body mount assembly of  FIG. 10 ; 
         FIG. 15  is a cross-sectional view taken along line  15 - 15  of  FIG. 14 ; 
         FIG. 16  is a perspective view of a cup member utilized with the body mount assembly of  FIG. 10 ; 
         FIG. 17  is a cross-sectional view of the cup member of  FIG. 16 ; 
         FIG. 18  is a cross-sectional view of a body mount assembly according to a third embodiment of the present disclosure; 
         FIG. 19  is a perspective view of an insert for use with the body mount assembly of  FIG. 18 ; 
         FIG. 20  is a cross-sectional view of the body mount assembly according to the principles of the present disclosure; 
         FIG. 21  is a second cross-sectional view of the body mount assembly of  FIG. 18 ; 
         FIG. 22  is a perspective view of an alternative cup member according to the principles of the present disclosure; and 
         FIG. 23  is a cross-sectional view of the cup member shown in  FIG. 22 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     With reference to  FIG. 1 , a vehicle body mount assembly  10 , according to the principles of the present disclosure, will now be described. The body mount assembly  10  is provided for connecting a support structure, such as a frame, vehicle cradle mount, or subframe  14 , to a vehicle body  12 . The body mount assembly  10  includes an insert  16  received in a micro-cellular urethane body member  18  which is partially surrounded by a cup member  20 . A fastener  22  engages a plate member  24  which is disposed against a lower end of the micro-cellular urethane body  18 . A nut  26  and washer  28  are provided for securing the support structure  14  to the body  12 . 
     With reference to  FIGS. 2-5 , the insert  16  will now be described. The insert  16  includes a generally cylindrical body portion  30  having an aperture  32  extending therethrough. The body portion  30  includes a first pair of radial projections  34 A,  34 B and a second pair of radial projections  36 A,  36 B which are offset from the first pair of radial projections  34 A,  34 B by 90 degrees. As shown in  FIGS. 2 ,  4 , and  5 , the first pair of radial projections  34 A,  34 B are taller in height than the second pair of radial projections  36 A,  36 B. Furthermore, the first pair of radial projections  34 A,  34 B have a maximum diameter D 1  which is greater than a maximum diameter D 2  of the second pair of radial projections  36 A,  36 B. Each of the radial projections  34 A,  34 B have a height H 1 , and the second pair of radial projections  36 A,  36 B have a height H 2 . It should be understood that the diameters D 1 , D 2  and heights H 1 , H 2  of the radial projections can be varied according to the desired design parameters. 
     With reference to  FIGS. 6 and 7 , the micro-cellular urethane body  18  and cup  20  assembly will now be described. The cup member  20  has a cylindrical body  40  having a first end  40 A provided with a radially outwardly extending flange  42  and a second end  40 B provided with a radially inwardly extending flange  44 . The micro-cellular urethane body  18  is over molded to the cup  20  and includes an aperture  48  extending axially therethrough wherein the aperture  48  is provided with a first pair of oppositely disposed recesses  50 A,  50 B and a second pair of oppositely disposed recesses  52 A,  52 B offset 90 degrees from the first pair of recesses  50 A,  50 B. The first pair of recesses  50 A,  50 B have a height H 3 , and the second pair of recesses  52 A,  52 B have a height H 4  which is less than the height H 3 . The first pair of recesses  50 A,  50 B have a maximum inside diameter ID 1  and the second pair of recesses  52 A,  52 B have a maximum inside diameter ID 2  which is smaller than ID 1 . 
     The micro-cellular urethane body  18  extends axially beyond the flange portion  42  of cup member  20  and extends radially outward so as to cover at least a portion of the face of the radially outwardly extending flange portion  42 . A second portion  56  of the micro-cellular polyurethane member  18  extends axially beyond the radially inwardly extending flange portion  44  of the cup member  20  so as to surround at least a portion of the radially inwardly extending flange portion  44 . The axially extending micro-cellular urethane portion  56  is disposed against the body member  12 , while the axially extending micro-cellular urethane portion  54  is disposed against the flat plate  24  between the support structure  14  and plate  24 . 
     The insert  16  is press-fit within the micro-cellular urethane body member  18  such that the diameter of the first pair of radial projections  34 A,  34 B is larger than the inside diameter ID 1  of the first pair of recesses  50 A,  50 B of the micro-cellular urethane body member  18 . Similarly, the diameter D 2  of the second pair of radial projections  36 A,  36 B is greater than the inside diameter ID 2  of the second pair of recesses  52 A,  52 B provided in the micro-cellular urethane body member  18 . Accordingly, the urethane body member is pre-compressed upon insertion of the insert  16  into the micro-cellular urethane body member  18  and cup assembly  20 . The amount of pre-compression of the micro-cellular urethane body member can be determined based upon design parameters and can be selected from a range of between 0 and 50 percent compression relative to the original uncompressed wall thickness dimension. A pre-compression amount of at least 10 percent is desirable in many applications. The amount of pre-compression increases the stiffness of the micro-cellular urethane body member  18  so as to provide desired characteristics in both the lateral and fore and aft directions. The height H 1 , H 2 , H 3 , H 4  can also be selected in order to selectively tune the height of micro-cellular urethane that is being pre-compressed. The body mount assembly of the present invention has been shown to provide high damping in the low frequency range and low damping in a high frequency range as is desired for optimal NVH conditions. 
     With reference to  FIGS. 10-17 , wherein like reference numerals are utilized with the added prefix  1  in order to designate common or similar elements to those described above, a second embodiment of the body mount assembly  110  will now be described. The body mount assembly  110  has a shorter height than the body mount assembly  10 , but utilizes an insert  116 , a micro-cellular urethane body member  118 , and a cup member  120  in a similar manner as described above. The insert  116  is shown including a first pair of radially extending projections  134 A,  134 B and a second pair of radial projections  136 A,  136 B that are each provided with the same height, with the radial projections  134 A,  134 B having a greater diameter than the diameter of the radial projections  136 A,  136 B. Other than that difference, the function and operation of the body mount assembly  110  is substantially the same as the body mount assembly  10 , as described above. Accordingly, a detailed description of the structure and function of the second embodiment of the body mount assembly  110  will not be provided. 
     With reference to  FIGS. 18-21 , a still further embodiment of the body mount assembly  210  will now be described. The body mount assembly  210  is provided for mounting the vehicle body  12  to a support structure  14  similarly to the previously described body mount assemblies  10 ,  110 . The body mount assembly  210  includes an insert  216  surrounded by an overmold micro-cellular urethane body member  218 . The insert  216  and over-molded micro-cellular urethane body member  218  are inserted into a cylindrical aperture  220  provided in the vehicle support structure  14 . A plate member  222  is provided between the body  12  and an upper portion of the insert  216 , and includes axially extending flange portion  222 A which is disposed against a separate micro-cellular urethane ring  224  which is also disposed against the support structure  14 . 
     As shown in  FIG. 19 , the insert  216  includes a radially extending flange base portion  230 , an axially extending post portion  232  that includes a first pair of radially extending projections  234 A,  234 B, and a second pair of radial projections  236 A,  236 B extending transverse to the first pair of radial projections  234 A,  234 B. An aperture  238  extends axially through the insert  216 . The micro-cellular urethane body member  218  is over molded around the insert  216  to provide a generally cylindrical outer surface surrounding the insert  216 . A radially extending flange portion  240  of the micro-cellular urethane  218  extends outward over the flange  230  of the insert  216 . In the assembled condition, as illustrated in  FIG. 18 , the micro-cellular urethane body member  218  is compressed from its original state, as illustrated in  FIGS. 20 and 21 , to a pre-compressed state, as illustrated by phantom lines A and B, as shown in  FIGS. 20 and 21 , respectively. As illustrated in  FIG. 20 , due to the wider diameter of the radially extending projections  234 A,  234 B as compared to the narrower diameter of the second pair of radial projections  236 A,  236 B, the micro-cellular urethane body member is pre-compressed to a greater extent, as shown in  FIG. 20 , than it is pre-compressed in the transverse direction, as shown in  FIG. 21 . 
     It should be noted that the relative direction in the fore, aft, and lateral directions can be specifically tuned to provide the desired NVH characteristics for a specific application. In addition, the assembly of the body mounts  10 ,  110 ,  210  also can provide pre-compression in the vertical direction via the tightening of the nut on the fastener  22  so as to pre-compress the axially extending portions  54 ,  56  of the body mount  10 ,  110 , or to compress the radially extending portion  240  and secondary ring  224  in the vertical direction. Thus, the body mount assemblies  10 ,  110 ,  210 , according to the principles of the present disclosure, are capable of providing lateral, fore, aft, and vertical NVH control with a simple light-weight construction. As described above, the amount of pre-compression can be selected in order to provide desired performance characteristics. In one exemplary embodiment, the amount of pre-compression in a first direction, either lateral or fore and aft, can preferably be approximately 25 percent of the wall&#39;s uncompressed thickness, while in the other transverse direction, the pre-compression can be approximately 33 percent. 
     In addition, in order to provide precision tuning of the body mount assemblies  10 ,  110 ,  210 , the body mount assemblies  10 ,  110 ,  210  can be tested for their vibration characteristics, and when deviating from desired characteristics, the cup members  20 ,  120 ,  220  can be selectively indented, as illustrated in  FIGS. 22 and 23 , to provide further precompression of the mirocellular urethane body  18 ,  118 ,  218  to precision tune the mount assembly for desired characteristics. The diameter and depth of the indentations  70  can be selected to provide the desired adjustments to obtain the desired characteristics. The use of indentation  70  to provide desired vibration damping characteristics can be used with or without pre-compression of the microcellular urethane body. In other words, the microcellular urethane body can be press-fit, simply inserted, or molded in place prior to the indentations  70  being formed in the cup member in order to achieve the desired characteristics. After the body mount is assembled, the vibration characteristics can be tested and compared to desired characteristics. If the vibration characteristics do not meet the desired characteristics, then the cup member can be selectively indented to adjust the vibration characteristics by compressing/or further compressing the microcellular urethane body.