Abstract:
A plug-in hydraulic body to frame mounting assembly is mounted to a conventional elastomeric body mount device to increase the control of vibration from the operation of the automotive frame to the automotive component supported thereon. The connecting member of the hydraulic mounting assembly threads onto the end of the fastener passing through the conventional elastomeric body mount device and anchors the outer can to a bridging can connected to the underside of the frame offrigger bracket to provide a true plug-n-go vibration control enhancement that can be added to any desired body mount location. The deflection of the fastener during operation of the elastomeric body mount device drives the operation of the hydraulic mounting assembly to dampen the deflection of the fastener in the elastomeric body mount corresponding to the transfer of operational loads between the body component and the offrigger bracket to which the body component is mounted.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. patent application Ser. No. 11/756,140, filed on May 31, 2007. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to the mounting of automotive body parts to a vehicle frame, and, more particularly, to an add-on hydraulic body mount device that can be coupled to an existing shear-style body mount to increase damping characteristics at desired locations on the vehicle frame. 
     BACKGROUND OF THE INVENTION 
     The body to frame mounting assembly is used to attach automotive body parts to a frame so that the two metal components do not directly contact one another, as a direct contact would provide a high degree of noise transmission from one component to another, as well as a direct transmission of vibration and other mechanical actions. Conventional body mount assemblies, compression or shear type, utilize multiple or single elastomeric members to isolate the frame from the automotive part to be mounted on the frame. Since both the frame and the automotive part are isolated from one another and from the fastener system joining them, the transmission of noise and vibration from the frame to the automotive part is minimized. 
     Controlling the design and material properties of typical body mounts, in reference to noise and vibration transmission to vehicle occupants, is only one, of many, paths that development engineering can take to address a total vehicle noise and vibration issue. Ultimately, the body mounting system is the direct transmission source of noise and vibration to the occupant compartment. Thus maintaining a body mount design that controls body movement and appropriately isolates the vehicle occupants from noise/vibration is challenging 
     In the design of automotive vehicles, such as pick-up trucks, the final desired vehicle level ride and vibration tuning requirements are complex in that consideration must be given to the multiple wheel base, power train, cab style, and tire/wheel offerings. Proper selection of material and isolator dynamic/static rates for tunable parts; i.e., suspension bushings, power train mounts and the body mounts, is critical when balancing vehicle level ride and vibration performance. Tunable part characteristic selection is one path, of many, that the vehicle engineering development community uses in establishing vehicle level performance attributes. The selected tuning can require multiple parts to support the complex vehicle offerings. Accordingly, while trying to maintain manageable component quantity complexity at the manufacturing facility, some vehicle configurations may not be optimally tuned for the best vehicle level ride and vibration performance. Couple vehicle build variability with individual component assembly variability and an opportunity exists to build a vehicle with less-than-optimal ride and vibration characteristics. At this point in development, time to make component design changes, for production, has elapsed to zero; trying to add more component/system damping becomes increasingly difficult. 
     The addition of frame mounted tuned mass dampers, to reduce vehicle level vibration sensitivity to Body-on-Frame vehicles, by adding increased levels of system damping, traditionally requires design proveout due to a late discovered issue. The design/development proveout requires a substantial amount of time and manufacturing expense to implement. Furthermore, the addition of mass dampers is effective only in select spots on the vehicle and requires additional development. Since the addition of mass dampers is not planned, the implementation represents a significant amount of additional expense. Generally speaking, frame mounted tuned mass dampers are affective once implemented; however, cost, weight and vehicle assembly are detrimental to the design. As mentioned previously, the output of a tuned mass damper still does not apply the desired damping at the best location; at the body mount positions. As such, hydraulic body mounts have been utilized in automotive vehicles as a replacement for the conventional body mount. These hydraulic mounts now add to the additional body mount/part complexity and also must adhere to the performance criteria of a traditional body mount such as, durable against high vehicle loads associated with vehicle operation, which has resulted in a high failure rate. 
     U.S. Pat. No. 5,330,166, granted to Hirofumi Aoli on Jul. 19, 1994, discloses a conventional hydro mount having a tunable frequency range that is used for classic engine, body or suspension mounts to replace shear-type body mounts, instead of being used in addition thereto. U.S. Pat. No. 5,529,295, issued to Markus Leibach on Jun. 25, 1996, is directed to an engine mount isolator employing an electromagnetic fluid controlled device to improve the feedback mechanism for an active controlled engine mount system. In U.S. Pat. No. 6,394,432, granted on May 28, 2002, to Gerald Whiteford, a conventional hydro mount system is provided with a compensator device to make up for the inherent shortcomings of the classic hydro mount. 
     U.S. Pat. No. 6,986,545, issued on Jan. 17, 2006, to Ingemar Nilsson, teaches the use of two isolators; however, the isolators are not joined together. Instead, the two isolators are joined to the same subframe member, but no pumping action from one isolator affects the driving of the other isolator. Accordingly, the Nilsson patent does not disclose a plug-in damper that is supplemental to the operation of the conventional isolator. In U.S. Pat. No. 7,036,803, issued to Clayton Maas on May 2, 2006, discloses an engine hydraulic mounting system with a switchable valve to avoid bulging of the main elastomeric unit. A two-stage isolation mount assembly is disclosed in U.S. Pat. No. 7,048,265, issued on May 23, 2006, to Anand Huprikar, to take advantage of a soft spring rate with a low maximum displacement. In U.K. Patent No. 2,343,665, a hydraulically damped engine mounting arrangement having two load-bearing mounts and two tie bars is disclosed. 
     None of the known prior art references teach a hydraulic body mount device that can be attached to a conventional shear-type body to frame mounting assembly to provide a tunable vibration damping function in which the conventional body to frame mounting assembly absorbs the high vehicle loads while the plug-in hydraulic body mount provides a supplemental damping effect to the conventional body to frame mounting assembly. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to overcome the aforementioned disadvantages of the known prior art by providing a plug-in hydraulic body mount that can be attached to a conventional body mount to enhance damping effects. 
     It is another object of this invention to provide a tunable body to frame mounting assembly in which a hydraulic body mount is attached to a conventional shear-type body mount. 
     It is a feature of this invention that a body to frame mounting assembly is tunable to enhance operation in reducing vehicle vibrations and noise transmission by the placement of supplemental hydraulic body mounts at those locations needing additional vibration damping. 
     It is an advantage of this invention that the hydraulic body mount is not required to absorb the loading imposed on the body to frame mounting assembly by the operation of the vehicle. 
     It is another advantage of this invention that the lack of vehicle loading in the hydraulic body mount device improves the failure rate associated with hydraulic body mounts. 
     It is another feature of this invention that the hydraulic body mount is affixed to the end of the fastener passing through the conventional shear-type elastomeric body mount device. 
     It is still another advantage of this invention that the plug-in hydraulic body mount device meets vibrational tuning requirements relating to multiple configurations of vehicle component offerings without requiring multiple tunable parts in the manufacturing process. 
     It is still another feature of this invention that effectiveness of the vibration control assembly in lesser customer base configuration selections are not hindered by the tunable vibration control devices configured for the highest customer base configuration selection. 
     It is yet another feature of this invention that the hydraulic body mount can be directly applied to the body-on-frame mount to increase damping ability of the conventional body mount device. 
     It is yet another advantage of this invention that the combination of the hydraulic body mount device to a conventional elastomeric body mount apparatus increases the potential to reduce vehicle level shake/sensitivity due to multiple component offering configurations. 
     It is a further advantage that the use of a hydraulic body mount device affixed to a conventional elastomeric body mount improves the manufacturing process for automotive vehicles by improving flexibility with respect to multiple vehicle configurations. 
     It is still a further advantage of this invention that the non-load bearing hydraulic body mounts avoid the inherent operational variability found in conventionally operable load bearing hydraulic body mount assemblies. 
     It is a further feature of this invention that the use of the plug-in hydraulic body mounts provides an easily tunable system that can be adapted to unique sensitivities, such as tire/wheel balance and the complexities of the many tire/wheel, power train and wheelbase combinations. 
     It is yet a further advantage of this invention that the plug-in hydraulic body mount is capable of being mounted on existing elastomeric body mounts and frame brackets and doesn&#39;t require their modification. 
     It is still another object of this invention to provide a plug-in hydraulic body to frame mounting assembly for use in attaching automotive components to a vehicle frame that is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use. 
     It is yet another advantage of this invention to eliminate any frame mounted tuned mass absorbers/dampers. 
     These and other objects, features and advantages are accomplished according to the instant invention by providing a plug-in hydraulic body to frame mounting assembly that can be mounted to a conventional elastomeric body mount device to increase the control of vibration from the operation of the automotive frame to the automotive component supported thereon. The connecting member of the hydraulic body to frame mounting assembly threads onto the end of the fastener passing through the conventional elastomeric body mount device and anchors the outer can to a bridging can connected to the underside of the frame offrigger bracket to provide a true plug-n-go vibration control enhancement that can be added to any desired body mount location. The deflection of the fastener during operation of the elastomeric body mount device drives the operation of the hydraulic body to frame mounting assembly to dampen the deflection of the fastener in the elastomeric body mount corresponding to the transfer of operational loads between the body component and the offrigger bracket to which the body component is mounted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages of this invention will become apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a perspective view of a representative vehicle frame having mounts for the attachment of automotive body components thereto; 
         FIG. 2  is an enlarged perspective view of a vehicle frame body mount to which an automotive part is being attached by a combination hydraulic and elastomeric body to frame mounting assembly incorporating the principles of the instant invention; 
         FIG. 3  is a cross-sectional view through the hydraulic plug-in body mount device taken along lines  3 - 3  of  FIG. 4  to depict the channel within the central member through which fluid flows when driven from the upper chamber into the lower chamber by the deflection of the fastener on which the hydraulic body mount is attached; 
         FIG. 4  is a cross sectional view of the combination hydraulic and elastomeric body to frame mounting assembly taken through the center of the body mount; 
         FIG. 5  is an elevational view of the hydraulic mount bridging can; and 
         FIG. 6  is a perspective view of the hydraulic mount bridging can shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, a vehicle frame containing offrigger brackets by which respective automotive parts and components, such as an underbody sheet metal floor pan cross member, are to be attached to the frame  10 . The frame  10  is representative of automotive frames to which appropriate automotive body parts or components are to be attached by connecting the body part or component  19  to a frame offrigger bracket  15 . As one of ordinary skill in the art will recognize, a vehicular frame  10  will be manufactured with a plurality of offrigger brackets  15  to secure the exterior sheet metal and other components  19  to the frame  10 . 
     Instead of directly bolting the automotive component  19  to the frame by a bolt fastening the component  19  to the corresponding offrigger bracket  15 , a substantial reduction of noise transmission from the road and other external sources through the frame  10  and mechanically transferred to the automotive component  19  can be accomplished by isolating the metal parts  10 ,  19  with an elastomeric material. In addition to a reduction in noise transmission, vehicle vibrations transmitted through the connecting joint are also significantly diminished. 
     This elastomeric joint has evolved into a body to frame mounting assembly in which an elastomeric member is connected to the vehicle body component  19 . In some body mount configurations, a lower elastomeric member can be provided to provide a two-piece body mount with the lower elastomeric member being connected to the frame offrigger bracket with a fastener, such as an attachment bolt, being inserted through a central opening through the upper and lower members. The attachment bolt clamps the elastomeric member between the outrigger bracket and the corresponding body component and provides a resilient mounting for the respective body component. The isolation material is typically selected from the group comprising, butyl rubber, natural rubber and micro cellular urethane, among others. 
     Referring now to  FIGS. 2-4 , the body to frame mounting assembly  20  can best be seen. The conventional shear-type elastomeric body to frame mounting assembly  21  is formed with an elastomeric member  22  that isolates the component  19  from the frame  10 . The elastomeric member  22  is formed with a central opening  23  extending therethrough to form a donut-like configuration through which an attachment bolt  25  passes. The automotive body part  19  to be mounted to the frame  10  is preferably formed to be engagable with the attachment bolt  25  and mated against the body mount top washer  26 . A body mount inner tube  27  passing through the central opening  23  engages the body mount lower washer  28  such that a bolt head or a nut  29  engaged with the attachment bolt  25  compresses the body mount lower washer  28  against the tube  27  and the body mount top washer  26 , which is engaged with the automotive component  19 . The elastomeric member  22  isolates the body mount top washer  26  and the tube  27  from the offrigger bracket  15 . 
     During normal operation, the elastomeric body mount  21  deflects as the operational loads are imposed on the frame  10  and the automotive component  19 , compressing the elastomeric member  22  and driving the attachment bolt  25  up and down relative to the offrigger bracket  15 . Thus, the loads transmitted between the offrigger bracket  15  on the frame  10  and the automotive component  19  pass through and are absorbed by the elastomeric body mount  21 . 
     To further dampen the vibrations passing between the frame offrigger bracket  15  and the automotive component  19 , the body to frame mounting assembly  20  further includes a supplemental hydraulic body mount  31  attached to the elastomeric body mount  21 . The hydraulic body mount  31  is formed with a steel connecting member  32  secured to an upper chamber  33  of a main elastomeric spring element that also includes a lower chamber  37 , which, in turn, is secured along the circumferential periphery thereof to a outer can  34 . The outer can  34  also supports a central member  35  having a fluid orifice track  36  formed therein to provide a passage of fluid through the central member  35 , and an lower chamber  37  of the main elastomeric spring element. A protective cap  38  is mounted on the lower chamber  37  to protect the main elastomeric spring element and provide room for the lower chamber  37  to expand. 
     The application of a hydraulic body mount  31  is determined by the desire to provide additional damping of vibration at any particular offrigger bracket  15 . The primary vibration control is provided by the elastomeric body mount  21 , as is the absorption of the operational loading between the frame  10  and the automotive component  19 . Where noise or vibration transmission at any particular point on the frame  10  needs to be further dampened, a hydraulic body mount  31  can be added to the elastomeric body mount  21  to enhance vibrational control. 
     Referring to  FIGS. 2-6 , to mount the hydraulic body mount  31  to a chosen elastomeric, shear-type body mount  21 , the hydraulic body mount  31  is positioned such that the connecting member  32  becomes engaged with the threaded lower end of the attachment bolt  25  extending below the bolt head or nut  29 . The rigid connecting member  32  is first threaded onto the attachment bolt  25  until the mating threads in the connecting member  32  bottoms out either by the attachment bolt  25  reaching the bottom of the connecting member  32  or the connecting member  32  reaching the bottom of the nut or bolt head  29 . The hydraulic body mount  31  is then compressed until the connection tabs  39  on the outer can  34  engage a mating slot  17 , preferably in the form of a bayonet slot to facilitate the mounting of the hydraulic body mount  31 , on a bridging can  16  attached to the offrigger bracket  15 . The compression of the hydraulic body mount  31  forces most of the fluid within the lower chamber  37  through the central member  35  into the upper chamber  33 . 
     In operation, the downward deflection of the attachment bolt  25  as described above with respect to the absorption of operational loads in the elastomeric body mount  21  is transferred to the connecting member  32  which, in turn, drives into the upper elastomeric chamber  33  and forces fluid to pass through the fluid orifice track  36  in the central member to pass into the lower chamber  37 . Conversely, the upward deflection of the attachment bolt  25  and attached connecting member  32  draws the fluid from the lower chamber  37  back into the upper chamber  33 . In either case, the compression against the fluid and the transfer thereof from one chamber  33 ,  37  to the other  37 ,  33 , dampens the movement of the attachment bolt  25  and, thus, enhances the control of the vibration transmission. Accordingly, the elastomeric body mount  21  drives the operation of the hydraulic body mount  31  so that the damping characteristics of the hydraulic body mount  31  are supplemental, and in addition, to the dampening characteristics of the elastomeric body mount  21 . Furthermore, the hydraulic body mount  31  does not bear any of the operational loads, which is borne by the elastomeric body mount  21 . 
     A typical condition in which the body to frame mounting assembly  20  incorporating the principles of the instant invention can be utilized is in steering wheel vibrations that often occur at speeds in excess of 45 MPH. Vibrational issues perceived by the driver of the vehicle can be excited in two conditions: (1) on smooth road surfaces at 55 MPH in conjunction with a first order tire or wheel uniformity load; and (2) on semi-smooth road surfaces (e.g. village roads) at 25 MPH due to single or multiple wheel input from small undulations on the road surface. However, in some component offerings, the mass damper is not completely satisfactory in resolving all of these vibration issues. 
     To provide enough system level damping to address such vehicle vibration issues, the hydraulic body mount  31  can be added at the best locations. The main damping effect of the hydraulic body mount  31  is actually a leveraged mass absorber effect, due to viscous damping caused by the moving fluid, generating the same performance as a 40 to 80 pound conventional mass absorber. By adding the hydraulic body mount  31  to the conventional shear-type body mount  21  connecting the cab structure to the frame, the vibrations are no longer transmitted into the cab structure and felt by the driver due to the exciting of the seat track from the transmitted vibrations. The hydraulic body mount uses the movement of the existing conventional body mount  21  to drive the fluid in the attached hydraulic body mount  31  and dampens the vibrations otherwise being transmitted into the cab structure. 
     In practice, the application of a hydraulic body mount  31 , as described above according to the principles of the instant invention, can be assembled into any selected vehicle configuration or provided as a service fix to address customer complaints relating to vibration issues, since the addition of the above-described hydraulic body mount  31  does not require any structural changes or component disassembly. Furthermore, the use of the hydraulic body mount  31  as described above avoids some of the pitfalls relating to failure of conventional utilization of hydraulic body mount devices, including high loading conditions, which is avoided due to the mounting of the hydraulic body mount  31  to an existing elastomeric body mount  21  instead of completely replacing the elastomeric body mount  21 , and the size of the body mount and the interaction with the frame or body component does not require changing. 
     It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention.