| 摘要 |
PROBLEM TO BE SOLVED: To provide an expansion type muffler which can be changed over between the normal service mode with low noise emission and the high output service mode using a simple structure and can prevent the emission of excessive exhaust noise by the two-stage expansion even in the high output service mode. SOLUTION: The inside of a casing 2 is partitioned by plates 6 and 7 so that a first expansion chamber 11 where an inlet pipe 14 is connected, a second expansion chamber 12 in communication to the first 11 through a communication pipe, and a third expansion chamber 13 which is in communication with the second expansion chamber 12 through a pipe and where an outlet pipe 15 is connected are formed to form an expansion type muffler, wherein a tubing 21 to generate communication between the first expansion chamber 11 and third expansion chamber 13 is installed on the partitioning plate, and an opening/closing valve 31 for this tubing 21 is installed.
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