Patent Application
20170044966
The present disclosure relates general to 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 even the ability to endure spike durability loads.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
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's exhaust system from the vehicle's body. In order to effectively isolate the vehicle's exhaust system from the vehicle's body, it is preferred that the isolator include a soft on-center rate of deflection.
The common prior art exhaust mounts or isolators have included two-hole pendulum rubber isolators which include 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 hanger. The metal stud hanger is often provided with an enlarged tapered head that can be forced through the aperture in the isolator, but which cannot be readily removed from the isolator. The opposite end of the hanger is welded to or otherwise secured to either a support point in the vehicle or to one of the components of the exhaust system.
Other designs for isolators include elastomeric moldings having a 1-hole spoke design wherein spokes are loaded in tension and compression, elastomeric moldings having a 1-hole shear leg design that include a pair of molded legs subjected to shearing in the primary loading direction, and elastomeric moldings having a bell-shaped design.
Most high temp elastomers utilized in exhaust isolator assemblies exhibit poor tensile fatigue properties stemming from low tear strength properties. It is therefore preferred to load the elastomeric material in compression or shear. For example, the puck design, as discussed above, provides for two pins to be inserted at opposite ends of the elastomeric element which allows loading in 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.
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. 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.
Shear leg design isolators have 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. 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.
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 vulnerable stress concentrations. While this has been achieved in the prior art shear-hub designs, stress concentrations at the ends of the voids continues to be an issue.
In one aspect the present disclosure relates to an isolator assembly for supporting an exhaust component from a structural portion of a vehicle. The isolator assembly may comprise a mounting bracket having a pair of spaced apart rings defining a mounting bore. An elastomer shear hub component may be disposed within the mounting bracket. The elastomer shear hub component may include an outer diameter (OD) shear hub extending between the pair of spaced apart rings, and an inner diameter (ID) shear hub disposed within the OD shear hub. The ID shear hub may define a central mounting bore adapted to receive an external hanger component.
In another aspect the present disclosure relates to an isolator assembly for supporting an exhaust component from a structural portion of a vehicle. The isolator assembly may comprise a mounting bracket having a pair of spaced apart circumferential rings defining a circular mounting bore. An elastomer shear hub component may be included which is disposed within the mounting bracket. The elastomer shear hub component may include an outer diameter (OD) shear hub extending between the pair of spaced apart rings, and an inner diameter (ID) shear hub disposed within the OD shear hub and connected to the OD shear hub via a transition portion. The ID shear hub may include a pair of ID shear hub portions extending in generally opposite directions that define a common, central mounting bore adapted to receive an external hanger component.
In still another aspect the present disclosure relates to an isolator assembly for supporting an exhaust component from a structural portion of a vehicle. The isolator assembly may comprise a mounting bracket having a pair of spaced apart circumferential rings defining a circular mounting bore, and a bottom wall having an aperture. An elastomer shear hub component may be disposed within the mounting bracket. The elastomer shear hub component may include an outer diameter (OD) shear hub extending between the pair of spaced apart circumferential rings, and an inner diameter (ID) shear hub disposed within the OD shear hub and connected to the OD shear hub via a transition portion. The ID shear hub may include a pair of mirror image ID shear hub portions extending in generally opposite directions that define a co-linear central mounting bore adapted to receive an external hanger component. The mirror image pair of ID shear hub portions may be coupled at an approximate midpoint along an axial length thereof to an approximate midpoint of the OD shear hub by the transition portion.
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.
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.
Referring now to the drawings, there is shown in
Exhaust system 10 comprises a muffler 14, an intermediate pipe 12, a catalytic converter 15, an exhaust hanger pin 16, a tailpipe 18 and a plurality of isolator assemblies 100 of various designs. Intermediate pipe 12 is typically connected to the engine or to a catalytic converter 15 which is then attached to an exhaust pipe which extends between the engine and the catalytic converter. The catalytic converter 15 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. In one alternative embodiment, intermediate pipe 12 can be attached to a plurality of catalytic converters which join together upstream of the muffler 14. In another alternative, the vehicle can have a plurality of exhaust pipes, a plurality of catalytic converters, a plurality of intermediate pipes and a plurality of mufflers which join together. It is further understood that an exhaust system may include a single tailpipe or multiple tailpipes. It should be further appreciated that, the exhaust system isolator of the present invention may be applied to any type of exhaust system including but not limited to dual exhaust systems having two parallel exhaust paths extending from the internal combustion system.
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 15 cleans the exhaust gases and muffler 14 quiets the noise created during the combustion process in the engine. The present invention is directed toward the exhaust system isolators 100 which mount exhaust system 10 to the vehicle while at the same time, isolate and damp the movement of exhaust system 10 with respect to the vehicle.
Referring now to
Referring now to
The elastomeric body 104 further comprises an OD shear hub 124, an ID shear hub 122, and a ground-out hub 126. The elastomeric body 104 defines a central mounting bore 110 which is designed to accept an inner tube, a bolt, or a hanger pin 16. Hanger pin 16 can further include a head and collar that act as hanger slide limiters. Hanger pin 16 is attached to a component of exhaust system 10. While bracket 102 is disclosed as being attached to a structural component of the vehicle and elastomeric body 104 is disclosed as being attached to a component of exhaust system 10, using hanger pin 16, it is within the scope of the present disclosure to have bracket 102 attached to exhaust system 10 and exhaust system isolator assembly 100 attached to a structural component of the vehicle using hanger pin 16. Thus, exhaust system 10 is secured to the vehicle through one or more exhaust system isolator assemblies 100.
Elastomeric body 104 includes a chamfer 130 located at one end of mounting bore 110. Chamfer 130 interfaces with the hanger pin 16. In at least one preferred embodiment, the chamfer 130 is tunable, typically ending flush to a leading edge of the isolator bracket 102. In at least one embodiment, the diameter of the chamfer is tuned such that the wall thickness of the OD shear hub 124 is equal to the wall thickness of the ID shear hub 122. Elastomeric body 104 defines a circumferential annular void 128. While annular void 128 is illustrated as being asymmetrical with respect to bracket mounting bore 112, it is within the scope of the present disclosure to have annular void 128 symmetrical with bracket mounting bore 112. The asymmetrical design for annular void 128 permits central mounting bore 110 to become disposed at or near the centerline of the bracket mounting bore 112 during the assembled or statically loaded condition of exhaust system isolator assembly 100. This is accomplished by molding mounting bore 110 vertically offset.
The design of both void 128 and chamfer 130, particularly the radial dimension of void 128 and the radial thickness of chamfer 130, will determine the distance a hanger pin disposed within the mounting bore 110 may radially translate with respect to the bracket mounting bore 112. Until the closing of void 128 and/or chamfer 130, the radial movements of central mounting bore 110 cause pure shear in elastomeric body 104 regardless of the loading direction. This shear loading occurs in the portion of elastomeric body 104 disposed between structural bracket mounting face 106 and hanger pin 16 as discussed below. Tuning for rate and deflection in selected directions can be accomplished independently from other directions by altering void 128 and chamfer 130 in the selected direction or by adding voids at specific circumferential positions of elastomeric body 104.
As can be seen in the figures, void 128 extends beyond bracket 102 and overlaps chamfer 130 in the axial direction to define the ID shear hub 122. The ID shear hub 122 which undergoes the shear loading due to the deflection of elastomeric body 104. During larger loading of exhaust system isolator assembly 100, void 128 and chamfer 130 will close and compressive stresses are imparted to elastomeric body 104 by the sandwiching of the ground-out hub 126 of the elastomeric body 104 between hanger pin 16 and bracket mounting bore 112. This contact between hanger pin 16, ground-out hub 126 and bracket mounting bore 112 eliminates the compression and thus the compression stresses on the OD shear hub 124 and the ID shear hub 122 when isolator assembly 100 experiences high ground-out loads. This improves both the performance and the reliability of exhaust system isolator assembly 100.
Exhaust system isolator assembly 100 avoids tension stress loading in the elastomeric body 104 during radial loading. The shear style loading in all directions enables exhaust system isolator assembly 100 to achieve a lower and more stable rate of deflection. This is because the shear modulus (shear loading) is lower than the elasticity modulus (tensile loading). Also, the spring rate of elastomeric materials in shear is more consistent than in tension. The rates and deflections are capable of being symmetrical about the center axis or they can be tuned using annular void 128 and chamfer 130 or by otherwise altering the size or shape of elastomeric body 104 or the rigid structures. An additional advantage is that the rate of deflection for ID shear hub 122 is linear throughout the deflection (until void 128 closes), which adds robustness to the design in regards to the position. This means that any pre-load from positional tolerances will not spike the rates of deflection and make the Noise, Vibration and Harshness (NVH) of the vehicle change with the exhaust geometry tolerances.
Referring to
Referring now to
The isolator 300 includes a mounting bracket 302 having a circular mounting bore 302a made up of axially aligned bores 302a1 and 302a2, and an elastomer shear hub component 304 which may be insert molded onto the mounting bracket 302. The mounting bracket 302 may be made from aluminum or any other suitably strong material which is resistant to the elements. In this embodiment the mounting bracket 302 has a unique configuration which includes dual, spaced apart circumferential rings 306 that help to form the mounting bore 302a. The rings 306 extend from sidewall portions 308 and merge into end walls 310. A bottom wall 312 of the mounting bracket 302 includes an aperture 314 through which a threaded shaft 318 of a fastener 316 is positioned. The fastener 316 enables the isolator 300 to be secured to an external mounting element associated with either an exhaust component or a structural portion of a vehicle. The fastener 316 also includes a head portion 320 which is shaped and of dimensions so that it resides in a pocket 322 of the mounting bracket 302, as best seen in
With further reference to
It will also be appreciated that while the rings 306 are shown in
The OD shear hub 324 and both of the ID shear hubs 326 are located between the end walls 310 of the mounting bracket 302 and thus do not extend axially outwardly from the end walls 310, as with the isolator 100. However, the OD shear hub 324 and the ID shear hub 326 could alternatively be formed such that one, or both, extend axially outwardly from the end walls 310 to further restrict sliding. The ID shear hubs 326 are further radially offset from a radial center of the mounting bore 302a. A central mounting bore 330 extends co-linearly through the ID shear hubs 326 to allow a portion of an external hanger to be received therein. The central mounting bore 330 is thus also radially offset from the radial center of the mounting bore 302a in order to provide a vertical offset for preload sag.
With further reference to
Referring to
An additional benefit of the isolator 400 of
Referring to
Referring to
While various embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the present disclosure. The examples illustrate the various embodiments and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.
This application claims the benefit of U.S. Provisional Application No. 62/203,659, filed on Aug. 11, 2015. The entire disclosure of the above application is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62203659 | Aug 2015 | US |
