| 摘要 |
PROBLEM TO BE SOLVED: To reduce the noise level of a centrifugal blower by suppressing the generation of a foreign sound near the tongue piece of a casing resulted from the rotation of blades of an impeller. SOLUTION: This sirocco fan (centrifugal blower) comprises the impeller 13 and the casing 1. The impeller 13 sucks gas from a side opening part and blows the gas to the centrifugal direction. The casing 1 comprises a gas outlet port 11a and a gas suction port opposed to the opening part of the impeller 13. The casing 1 covers the impeller 13 so as to form a spiral air passage 10a connected to the gas outlet port 11a between it and the impeller 13. In the casing 1, a flat part 62 is formed in the tongue part 60. The tongue part 60 is the vicinity part of a closest part 60a closest to the circumferential end of the impeller 13.
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