Abstract: An impeller is provided for a blower having a blade (15), a plurality of notches (17) provided at predetermined intervals on a side edge of the blade (15), and a plurality of smooth portions (18) each provided between a pair of the notches (17). Since a transverse vortex discharged from the side edge of the blade (15), and on a large scale, is organized by vertical vortexes formed in the notches (17) on a small scale so as to be segmented into stable transverse vortexes, it becomes possible to reduce aerodynamic noise.

Abstract: The present invention provides a centrifugal fan by which air velocity distribution in the height direction of impellers at a fan blow-out port is made uniform and running noise is reduced, and an air conditioner whose running noise is reduced by applying the centrifugal fan thereto. The centrifugal fan is provided with a hub for fixing the rotary shaft of a motor, a main plate formed on the outer circumference of the hub, a shroud disposed to be opposed to the main plate, which forms an air passage, a plurality of impellers disposed between the main plate and the shroud, and a bellmouth disposed at the suction side of the shroud. Projections or recesses are formed on the surface of the shroud facing the bellmouth, which projections or recesses form air streams flowing from the center of the shroud toward the outer circumference thereof along the surface when running a fan. The air conditioner has a thus constructed centrifugal fan mounted therein.

Abstract: An impeller is provided for a blower having a blade (15), a plurality of notches (17) provided at predetermined intervals on a side edge of the blade (15), and a plurality of smooth portions (18) each provided between a pair of the notches (17). Since a transverse vortex discharged from the side edge of the blade (15), and on a large scale, is organized by vertical vortexes formed in the notches (17) on a small scale so as to be segmented into stable transverse vortexes, it becomes possible to reduce aerodynamic noise.

Abstract: A frame (4a) is provided around the perimeter of the air outlet (2a) of the fan (6). The frame (4a) includes a plurality of board-shaped ribs (41, 41 . . . ) extending radially outward from the vicinity of the center of the frame (4a) in the direction of the radius of the fan (6). The frame (4a) also includes a plurality of cylindrical ribs (42, 42 . . . ) integrated with the plurality of board-shaped ribs (41, 41 . . . ), and arranged concentrically around the rotation axis (O-O′) of the fan (6) at predetermined intervals in the direction of the radius of the fan (6). The board-shaped ribs (41) are curved outward in the direction of rotation of the fan (6) and inclined in the direction of air flowing from the fan (6).

Abstract: In an axial fan having a plurality of blades (2, 2, . . . ) around an outer periphery of a hub (1), a cross-sectional configuration of each of the blades (2) at an arbitrary distance from a center of the fan is set such that a blade thickness gradually increases moving away from a blade leading edge (2a) and then gradually decreases towards a blade trailing edge (2b). Also, if a length of a camber line extending from the blade leading edge (2a) to a position where the blade thickness becomes maximum is taken to be L, and a length of a camber line extending from the blade leading edge (2a) to the blade trailing edge (2b) at the arbitrary distance is taken to be L.sub.0, then L/L.sub.0 falls within a range of 0.27 to 0.35. Thus, the aerodynamic performance never lowers even if the inflow angle of air into the blade (2) varies.