Importance

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Abstract

In the exhaust fluid path, there are provided a porous pipe that is in communication with a muffling chamber via a plurality of small through-holes formed across a wall thickness of the pipe, and an inner pipe of a given length is inserted in the porous pipe with a gap formed between the outer surface of the inner pipe and the inner surface of the porous pipe. The gap is narrowed or closed in its outlet portion and thus the exhaust sound waves flowing through the gap are compressed so that interference and scattering into the muffling chamber of the exhaust sound waves via the small through-holes are promoted, thereby enhancing muffling performance. A plurality of small through-holes may also be formed in the inner pipe. A relatively large opening may be formed in part of the porous pipe to open into the muffling chamber, or a relatively large space may be formed which divides the porous pipe into two pipe elements and opens into the muffling chamber. The porous pipe may be formed as a dual-pipe structure to provide a triple-pipe structure as a whole. Another alternative arrangement may be such that the muffling chamber is partitioned by a wall having a plurality of small through-holes so as to provide a sub-chamber and that the tubular exhaust path opens into the sub-chamber so as to enhance exhaust efficiency.

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First Claim