| 摘要 |
PURPOSE:To prevent sound transmission by affording and shutting off communication between a silencer expansion chamber communicating to the upstream side are bypass path and the downstream side are bypass path by a duty ratio controlling electromagnetic valve and setting the ratio of the volume of said chamber to the area of said upstream side bypass path to a predetermined value. CONSTITUTION:In the normal travelling, an air controlling valve 2 is closed and a duty ratio controlling electromagnetic valve 1 is operated so that auxiliary air is sent to a silencer expansion chamber 12 from air bypassing path P3 through an air introducing path P3' and supplied to an engine E through an air introducing port 17, an air discharging port 18, an opening P4' and an air bypass path P4. An amount of supply of the auxiliary air is proportional to the duty ratio of a valve body 16 operated repetitively with high speed, so that the rotational frequency of the idling engine is maintained constant. Intake vibration sound in the operation of said valve 1 is effectively reduced by the predetermined ratio of the volume of said chamber 12 to the area of said path P3 so that it is hardly transmitted to the bypath path P3. |
