Patent ID: 8075262

Claim:
A centrifugal-type blower comprising: a rotatable shaft; a centrifugal-type multiblade fan having a plurality of blades around the rotatable shaft; and a casing having an involuted shape and accommodating the fan, the casing including: a volute start part and a volute end part of the involuted shape; an inlet for air on one end side of the casing in an axial direction of the rotatable shaft; an air passage on an outer circumferential side of the fan; and a side wall part radially outward of the fan, wherein: the side wall part, the fan, the volute start part, and the volute end part define the air passage; the side wall part includes an inlet side end portion on a side of the inlet, a counter-inlet side end portion on an opposite side from the inlet, and an intermediate position between the inlet side end portion and the counter-inlet side end portion in the axial direction of the rotatable shaft; a first distance from a center of the fan to the side wall part at the inlet side end portion thereof in a radial direction of the fan gradually increases from the volute start part to the volute end part in a rotational direction of the fan; a second distance from the center to the side wall part at any position thereof from the intermediate position to the counter-inlet side end portion in the radial direction of the fan is larger than the first distance within a first range from the volute start part to a predetermined position, which is located halfway from the volute start part to the volute end part, in the rotational direction of the fan except the predetermined position; the second distance gradually decreases from the volute start part to the predetermined position; and the second distance has a same length as the first distance within a second range from the predetermined position to the volute end part in the rotational direction of the fan.