| 摘要 |
An improved supercharger or blower (10) of the Roots-type with reduced airborne noise. The blower includes a housing (12) defining generally cylindrical chambers (32, 34) containing meshed lobed rotors (14, 16) mounted for rotation about parallel, transversely spaced apart axes. The rotor lobes (14a, 14b, 14c, 16a, 16b, 16c) are formed with an end-to-end helical twist according to the relation 360 DEG /2n, where n equals the number of lobes per rotor. Blower housing (12) also defines inlet and outlet ports (36, 38) having transverse and longitudinal boundaries. Spaces (32a, 34a) between adjacent lobes of each rotor transfer volumes of low-pressure inlet port air to relatively high-pressure outlet port air. The longitudinal boundaries of the inlet port are defined by transversely extending wall surfaces (20f, 20h) and the transverse boundaries are defined by wall surfaces (20g, 20i) disposed substantially parallel to the associated rotor lobes. The longitudinal boundaries of the outlet port are defined by transversely extending wall surfaces ( 20m, 20p) and the transverse boundaries are defined by wall surfaces (20n, 20q) extending between transversally extending wall surfaces (20m, 20p). Wall surfaces (20n, 20q) respectively include surface portions (20r, 20t) and (20s, 20u) which give the port a somewhat hourglass shape effectively dividing the port into controlled backflow areas via expanding orifices (42, 44) and into an unrestricted outflow area.
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