| 摘要 |
PROBLEM TO BE SOLVED: To improve a silencing effect in a low rotational speed region of an engine, by providing an energizing means applying a closing directional load to act in a butterfly valve to a prescribed opening from its fully closed condition, in the butterfly valve opening operated by a flow of exhaust gas. SOLUTION: In a low rotational speed region of an engine, valve closing force by a return spring 12 is strong, to hold a butterfly valve 10 in a closed condition, so as to ensure a function as a low frequency resonance chamber of an inner pipe. However, in accordance with the increasing of an engine speed, a dynamic pressure of exhaust gas rises, when the butterfly valve 10 is started to open, a link 17 is turned downward, but until its connecting pin 18 leads to a turn over position A, a compression spring 23 is compressed, its extension force acts in a closing direction of the butterfly valve 10. When the connecting pin 16 passes through the turn over position, the link 17 is turned downward, the butterfly valve 10 is opened. |
