| 摘要 |
PROBLEM TO BE SOLVED: To provide a Roots type supercharger which is capable of suppressing noise caused by reverse flow to the minimum, reducing pressure fluctuation, and improving heat insulation temperature efficiency, and to provide its noise reducing method. SOLUTION: A plurality of reverse flow ports 10a, 10b, 10c whose areas for penetrating a casing are different from each other, are disposed on a position close to a delivery port and close to an end surface of a reverse delivery port side of a rotor. The reverse flow ports are arranged at clearances from an upstream side in order of small area. Reverse flow is carried out by opening the reverse flow ports in order of small area while communicating in order so as to reduce noise.
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