| 摘要 |
PROBLEM TO BE SOLVED: To provide a low-cost supercharger that reliably reduces noise despite a simple structure while ensuring a high engine output response. SOLUTION: The supercharger 4, which is driven by given power to pressurize an air supply to an engine 3 and arranged upstream of a throttle valve 6, is provided with a bypass passage 7 for connecting a discharge port to a suction port of the supercharger 4. An on-off valve 9 designed for larger opening with increasing output of the engine 3 is arranged upstream of the supercharger 4. Despite an appreciable output response ensured by the arrangement of the throttle valve 6 just before the engine 3, while the output of the engine 3 is low with the bypass passage 7 opened, even if a pulsating sound or the like emitted from the supercharger 4 flows back to an upstream side of the supercharger 4 via the bypass passage 7, the on-off valve 9 that is closed prevents external leakage through an air cleaner 1 and the like to thereby effectively prevent generation of grating noise such as a pulsating sound during low output.
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