| 摘要 |
PROBLEM TO BE SOLVED: To enhance silencing function in a low speed range of an engine, to reduce back pressure in a middle speed range and to further reduce the back pressure in a high speed range. SOLUTION: A first exhaust outlet pipe 12 incorporated with a first shut-off means 13 is merged thereinto with a second exhaust outlet pipe 18 having a diameter smaller than that of the first exhaust outlet pipe 12 and having a length suitable for silencing in a low speed range of an engine, downstream of the first shut-off means 13. A chamber 6 to which an exhaust inlet port of the first exhaust outlet pipe 12 is opened, is communicated with a chamber 7 upstream of the chamber 6 through a communication pipe 16 and a bypass pipe 19, and a second shut-off means 17 is provided for opening and closing the communication pipe 16. The diameter of the bypass pipe 19 is set smaller than that of the communication pipe 16. After the first shut-off means 13 is opened, the shut-off means 17 is opened. |
