Centrifugal blower, air conditioning device, and refrigeration cycle device

Abstract

A centrifugal blower (1) comprises: a fan (2) in which a plurality of blades are mounted to a peripheral edge portion of a main plate and which generates an airflow by rotation; and a scroll casing (4) in which the fan is accommodated. The scroll casing has a peripheral wall (4c) provided in a spiral shape so as to form, between the peripheral wall and an outer peripheral portion of the fan, a gap serving as an air passage for converting dynamic pressure of the airflow generated by the fan into static pressure. When viewed from one side of the rotation axis of the fan, reduced portions (12, 13) in which the gap is reduced are provided at two opposing locations in the peripheral wall. When viewed from one side of the rotation axis, the peripheral wall has the first reduced portion (12), the second reduced portion (13) provided on the downstream side of the first reduced portion in a flow direction of the airflow in the air passage, and a curved intermediate portion (14) connecting the first reduced portion and the second reduced portion. At least one of the first reduced portion and the second reduced portion has a thin wall portion (4c1) in which the wall thickness of the peripheral wall is reduced so as to expand the gap, in a portion in the axial direction in which the rotation axis extends.

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