Patent ID: 8562297

Claim:
A centrifugal fan comprising: an electric motor including a rotary shaft; and an impeller coupled to the rotary shaft of the electric motor to rotate therewith and having a suction port opened in an axial direction of the rotary shaft for sucking air and a plurality of discharge ports for discharging the sucked air in a radial direction of the rotary shaft, the impeller including: a hub coupled to the rotary shaft and extending in the radial direction of the rotary shaft; a shroud facing an outer peripheral portion of the hub and formed with the suction port at a central portion thereof; and a plurality of blades arranged between the outer peripheral portion of the hub and the shroud at intervals in a direction of rotation of the rotary shaft, wherein: each of the discharge ports is formed between radially outer ends of adjacent two of the blades; each of the blades includes a curved portion at a corner formed between a positive pressure surface thereof and the shroud, the curved portion having a curvature that gradually decreases toward a corresponding one of the discharge ports; the curved portion includes a curved surface that is curved to be concave in the direction of rotation and outwardly in the radial direction, and forms a part of the positive pressure surface; an airflow path is formed by the outer peripheral portion of the hub, the positive pressure surface of one of the two adiacent blades, a negative pressure surface of the other of the two adiacent blades, and the shroud; a sectional contour of the curved surface, as the curved portion is sectioned in a direction orthogonal to the direction of rotation, is constituted from a linear line segment and a curved line segment in a location distant from the discharge port; the linear line segment gradually decreases toward the discharge port while the curved line segment gradually increases toward the discharge port; and in the vicinity of the discharge port, the sectional contour of the curved surface is constituted from the curved line segment alone.