Patent Application
20060037811
1. Field of the Invention
The present invention relates generally to muffler assemblies, and more particularly to motorcycle muffler assemblies.
2. Description of the Related Art
Muffler assemblies are known. Exemplary muffler assemblies are disclosed, for example, in U.S. Pat. Nos. 4,574,914; 5,183,130; 5,979,583; and 6,267,193, which are all incorporated by reference herein in their entirety. Other muffler assemblies also exist.
When designing a muffler, it is advantageous to achieve a relatively high gas flow rate, as increased gas flow often leads to an increase in engine performance. However, increasing the gas flow rate also tends to decrease a given muffler's sound dampening performance. Hence, known muffler assemblies tend to be either quiet and low performing, or loud and high performing. Thus, a need exists for an improved muffler assembly that is relatively quiet, with an improved gas flow rate.
The aforementioned problem of designing a quiet, high performance muffler is particularly difficult in applications involving relatively tight size and orientation constraints. By way of example, in motorcycle applications it may be desirable to hide as much of the muffler assembly as possible for cosmetic reasons. Similarly, it may be desirable to orient exposed regions in such a way that more aesthetically appealing portions (e.g., chromed surfaces) are the regions most readily visible by a bystander, again for cosmetic reasons. Similar considerations may apply in other contexts, such as all terrain vehicles (ATVs), snowmobiles, boats (particularly with inboard engines), and jet skis. In these applications, it is even more difficult to achieve a relatively quiet, high performance muffler without adversely impacting the vehicle's aesthetics.
Other problems with the prior art not described above can also be overcome using the teachings of the present invention, as would be readily apparent to one of ordinary skill in the art after reading this disclosure.
Reference will now be made in detail to exemplary embodiments of the present invention. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
A muffler assembly for a motorcycle according to an embodiment of the present invention is shown in
As shown in
The diffuser section 110, which can also be generally referred to as a first chamber of the muffler assembly, is adapted to expand exhaust gas entering the muffler assembly via exhaust inlet 140. Preferably, the diffuser section 110 extends from a first end 150 of the muffler assembly toward a second end 160 of the muffler assembly, and is the front-most section of the muffler assembly (not including exhaust inlet 140). According to one aspect of the present invention, the angled portion of the diffuser section 110 is about 3.00″ or more in length (i.e., the length from the first end 150 toward the second end 160 parallel to a central axis of the muffler assembly).
As shown best in
The center line of the exhaust inlet 140 may be offset from a centerline of the diffuser section 110 as shown. In this regard, the center line offset may be in the range of about 1″ to about 1.5″, preferably about 1.25″. Due to this center line offset, the inner wall 112 has a departure angle away from the exhaust inlet 140 at a first angle θ1, on a first side, and at a second angle θ2 on a second side. Preferably, first angle θ1, is in the range of about 40° to about 50°, more preferably about 42.67°. Preferably, second angle θ2 is in the range of about 10° to about 15°, more preferably about 11.20°. Additionally, it should be appreciated that, while only angles in reference to inner wall 112 have been discussed, the inner wall 112 may be substantially parallel to the outer wall 114. Furthermore, one or both of inner wall 112 and/or outer wall 114 may be angled up to about 5.00″ into the muffler assembly, though preferably up to about 3.00″ as previously discussed.
As shown best in
In manufacturing diffuser section 110 and/or muffling section 120, a sheet metal material may be used. In this regard, the sheet metal material may be rolled to achieve a substantially obround shape, as shown, for example, in
As shown best in
It should be appreciated that one or more components of the removable end cap 130 (e.g., the insert 134) may extend into a third chamber of the muffler assembly, or the third chamber may be eliminated altogether. Preferably, however, no component of the removable end cap 130 substantially extends into the muffling section 120 of the muffler assembly. In this regard, the muffling section 120 is kept baffle free, so as to maximize a flow rate of exhaust through the muffler assembly. Other configurations including one or more baffles in any one or multiple of the three sections are also contemplated, as shown in the exemplary cross sections of
According to one embodiment of the present invention, an insulating material 166 is provided between the inner and outer walls 112, 114 and/or 122, 124 of the diffuser section 110 and muffling section 120 respectively. Preferably, at least ⅛″ thick insulating material 166 is used for such an application. The insulating material 166 is provided to reduce heating of the outer wall 114 and/or 124 due to the temperature of the exhaust gas. By reducing heating of the outer wall 114 and/or 124, heating related discoloration of the outer wall 114 and/or 124 can be reduced or eliminated. Insulating materials such as fiberglass or steel wool may be used, though other materials are also contemplated.
The present inventors have further discovered that, for muffler assemblies having the same outer volume as previously described assemblies, thicker insulating materials 116, such as insulating materials at least ⅜″ thick may be used and provide some advantageous results. Specifically, while a slight reduction in inner volume may be required to accommodate the thicker insulating materials, the present inventors have discovered the thicker insulating material does not substantially reduce performance of the muffler assembly, yet achieves a deeper exhaust tone and quieter overall sound level in comparison to a muffler assembly with ⅛″ thick insulating material. Hence, according to one embodiment of the present invention, an insulating material 166 at least ⅜″ thick is provided. According to another embodiment of the present invention, insulating material 166 has a thickness in the range of about ⅛″ thick to about ⅜″ thick. Other configurations are also contemplated.
The present application may be used to construct a motorcycle muffler assembly with an interior volume (e.g., the region inside of inner wall 112, 114) of about 325 cubic inches, using an outer obround shaped periphery of about 6.25″× about 3.25″. Such a configuration may achieve a sound reduction of more than 3 dB in comparison to known motorcycle muffler assemblies, with improved overall gas flow throughput. Other configurations are also contemplated.
A muffler assembly 800 according to another embodiment of the present invention is shown in
The foregoing description of various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.
