| 摘要 |
An improved supercharger or blower (10) of the Roots-type with reduced airborne noise and improved efficiency. The blower includes a housing (12) defining generally cylindrical chambers (32, 34) containing meshed lobed rotors (14, 16) having the lobes (14a, 14b, 14c, 16a, 16b, 16c) thereon formed with an end-to-end helical twist according to the relation 360 DEG /2n, where n equals the number of lobes per rotor. The chambers include cylindrical wall surfaces 20a, 20b and end wall surfaces 20c, 24a which sealing cooperate with the rotor lobes and ends. Blower housing (12) also defines inlet and outlet ports (36, 38). The inlet port includes a longitudinal extent defined by housing wall surfaces (20f, 20f) and a transverse extent defined by housing wall surfaces 20g, 20i. Transverse wall surfaces (20g, 20i) are disposed substantially parallel to the associated rotor lobes. The outlet port includes a longitudinal extent defined by housing surfaces (20m, 20r) and a transverse extent defined by housing surfaces (20p, 20s). Spaces (32a, 34a) between adjacent lobes of each rotor transfer volumes of low-pressure inlet port air to relatively high-pressure outlet port air. Associated with the outlet port are first and second expanding orifices (42, 44) disposed on transversely opposite sides of the outlet port for controlling the rate of backflow into the transfer volumes and operative at predetermined rotor speed and pressure differential relationships to maintain a substantially constant backflow rate into each of the transfer volumes. Pairs of arcuate channels 46, 48 and 58, 60 are respectively formed in end walls 20c, 24a to vent trapped volumes SIGMA TV1 and SIGMA TV2 defined by meshing lobes. Channels 46, 48 prevent compression of air in trapped volumes SIGMA TV1 and channels SIGMA TV2 prevent vacuum tending expansion of trapped volumes SIGMA TV2.
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