Acoustics – Sound-modifying means – Muffler – fluid conducting type
Reexamination Certificate
2000-07-27
2001-09-11
Dang, Khanh (Department: 2837)
Acoustics
Sound-modifying means
Muffler, fluid conducting type
C181S272000
Reexamination Certificate
active
06286623
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to sound-attenuating mufflers for internal combustion engines and, more particularly, to sound-attenuating mufflers generating reduced back pressure.
Numerous muffler constructions have been proposed for the attenuation of the sound component of an exhaust gas stream from an internal combustion engine. Such mufflers are designed towards achieving appreciable sound attenuation, but without substantially increasing the back pressure on the engine, which results in power loss, reduced engine efficiency, and higher fuel consumption.
In surveying the prior art, U.S. Pat. No. 4,574,914 to Flugger teaches that although the patent art contains various muffler constructions which purport to solve the problem of sound attenuation without undesirable back pressure, in reality these various structures have substantial performance deficiencies. It is well known to provide a divergently tapered centrally located conical partition for flow of gases around the partition to effect an expansion of the gases. Typical of such structures are the devices shown in U.S. Pat. Nos. 2,071,351, 2,239,549 and 2,971,599.
Some of these patented mufflers follow such an expansion partition or cone with a contraction or concentrating partition or baffle. Typical of such devices are the mufflers shown in U.S. Pat. Nos. 1,081,348, 2,667,940, 3,029,895 and 3,029,896. These mufflers, however, do significantly increase back pressure by causing the exhaust gases to reverse the direction of their flow axially as they attempt to pass beyond the concentrating or converging baffle. This flow reversal may be effective in sound attenuation, but it has been found to increase back pressure undesirably.
Even mufflers which employ alternating divergent and then convergent partitions have suffered from undesirable bulk and/or weight, inordinate complexity, or auxiliary flow channels or openings in the partitions which defeat sound attenuation. Typical of such mufflers are the mufflers set forth in U.S. Pat. Nos. 624,062, 1,184,431, 2,325,905 and 2,485,555.
Thus, U.S. Pat. No. 4,574,914 to Flugger concludes that while the successive outward deflection and then inward convergence of gases in a muffler is broadly known in the prior art, such prior art structures typically have partitions or baffle structures which induce undesirable back pressure, contain openings or passageways which diminish the sound attenuating effectiveness of the muffler, or require excessive length, diameter and/or weight.
The inventive muffler disclosed in U.S. Pat. No. 4,574,914 to Flugger is a compact, sound-attenuating muffler for a high-performance internal combustion engine in which the muffler casing has an elongated transverse cross-section with a height dimension of only slightly larger than the height dimension of the inlet exhaust pipe and a width dimension in the range of about 2 to 4½ times the height dimension. The muffler includes a divergently tapering planar first partition which causes gases to be expanded only in a horizontal plane toward the side walls of the muffler and further includes a second partition formed to contract or converge the gases in a horizontal plane toward a central opening. The first partition has a cup-shaped back surface so that contraction of the gases around the back side of the first partition is highly effective in attenuating sound, and both partitions are sloped in a direction toward the outlet from the muffler so as to minimize the generation of back pressure, which is not substantially greater than the back pressure in a straight pipe.
The muffler disclosed in U.S. Pat. No. 4,574,914 is designed explicitly for high-performance internal combustion engines for racing cars and the like. Although the back pressure generated by such mufflers is reported to produce a power loss of less than 2%, the sound level reduction associated with this power loss is from 130 db on the A scale to about 90 db on the A scale. A sound level of about 90 db on the A scale is completely unacceptable for common passenger vehicles and the like.
There is therefore a recognized need for, and it would be highly advantageous to have, an exhaust system providing a combination of improved sound attenuation and reduced back pressure generation, yet is simple, compact, lightweight, and easy to fabricate.
SUMMARY OF THE INVENTION
According to the teachings of the present invention there is provided a muffler for an internal combustion engine having characteristically low back pressure and a pleasing sound. The muffler comprises: (a) an elongated housing having an interior wall and including: (i) an inlet opening formed for the flow of exhaust gas into the housing, and (ii) an outlet opening formed for the discharge of exhaust gas from the housing; and (b) a partition shaped like a hollow pyramid, disposed in the housing and having interior surfaces and exterior surfaces, the exterior surfaces joining at a first end to form a pyramidal apex, the pyramidal apex pointing toward the inlet opening, and extending at a second end to form a rugose base, wherein the partition is disposed in the housing to form a plurality of spaces between the rugose base and the housing for the flow of exhaust gas.
According to further features in the described preferred embodiments, the flow of exhaust gas through the inlet opening is directed towards the pyramidal apex, thereby causing the flow of the exhaust gas to be, and wherein the exhaust gas flows across the rugose base of the exterior surfaces before being discharged through the outlet opening.
According to yet another aspect of the present invention there is provided a muffler for receiving and discharging a flow of exhaust gas from an internal combustion engine, the muffler comprising: (a) an elongated housing having an interior wall, the housing including: (i) an inlet opening formed for the flow of exhaust gas into the housing, and (ii) an outlet opening formed for the discharge of exhaust gas from the housing; and (b) a partition disposed in the housing and having interior surfaces and exterior surfaces, the exterior surfaces joining at a first end to form an apex, the apex pointing toward the inlet opening, and flaring out at a second end to form a rugose base, wherein the partition is disposed in the housing to form a plurality of spaces between the rugose base and the housing for the flow of exhaust gas, and wherein the flow of exhaust gas through the inlet opening is directed towards the apex, thereby causing the flow of the exhaust gas to be deflected along the exterior surfaces and towards the interior wall of the housing, and wherein the exhaust gas flows across the rugose base of the exterior surfaces before being discharged through the outlet opening.
According to still further features in the described preferred embodiments, the flow of the exhaust gas is deflected along the exterior surfaces in substantially all directions.
According to still further features in the described preferred embodiments, a first portion of the exhaust gas flows directly beyond the rugose base, and a second portion of the exhaust gas flows in a substantially reverse fashion along the interior surfaces. According to still further features in the described preferred embodiments, the ratio of the second portion to the first portion is between 0.1 to 1.0 and 0.3 to 1.0.
According to still further features in the described preferred embodiments, the plurality of spaces includes at least one space having an inverted V shape.
According to still further features in the described preferred embodiments, the partition has a plurality of ears extending from the rugose base, each of the plurality of ears substantially contacting the housing, thereby providing no-flow zones between the plurality of spaces.
According to still further features in the described preferred embodiments, the interior wall is substantially curvilinear or substantially rectangular.
According to still further features in the described preferred embodiments, the muffler further comp
Dang Khanh
Friedman Mark M.
Silent Exhaust Systems Ltd.
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