Patent ID: 8870541

Claim:
A centrifugal multiblade fan for drawing air from one end side of the fan in an axial direction of the fan and for blowing out the air radially outward of the fan, the fan comprising: a rotatable shaft; a plurality of blades arranged around the rotatable shaft, wherein: each of the plurality of blades includes: a corresponding positive pressure surface located on a front side thereof in a rotational direction of the rotatable shaft; a corresponding negative pressure surface located on a rear side thereof in the rotational direction; and a corresponding front edge located on a front side thereof in a radially inward direction; and the front edge includes a corner part on a positive pressure surface-side thereof and a corner part on a negative pressure surface-side thereof; a side shroud coupling together respective end portions of the plurality of blades on the one end side; and a main shroud joined to the rotatable shaft and coupling together respective end portions of the plurality of blades on the other end side of the fan in the axial direction, wherein: the front edge has a shape that is inclined radially outward in a direction from the main shroud toward the side shroud; and provided that: a cross section, along which a side shroud-side region of each of the plurality of blades is cut in a direction perpendicular to the rotatable shaft, is a reference cross section; a curve, which appears when the positive pressure surface is cut along the reference cross section, is a positive pressure surface reference curve; and the corner part on the positive pressure surface-side, which is on the reference cross section, is a positive pressure surface side reference corner part, when viewed from the axial direction, the corner part on the positive pressure surface-side is located on a tangential line of the positive pressure surface reference curve at the positive pressure surface side reference corner part, and when viewed from the axial direction, a curvature radius of the negative pressure surface becomes larger in the axial direction from the side shroud toward the main shroud when a comparison is made between the curvature radius of the negative pressure surface at a side shroud side portion and the curvature radius of the negative pressure surface at a main shroud side portion, the side shroud side portion and the main shroud side portion are located at the same position in a radial direction of the fan.