As for a conventional fan, for example, Japanese Patent Laying-Open No. 2008-241188 discloses a cross-flow blower aimed at reducing separation of the flow-in air while preventing a surging phenomenon or a reverse intake phenomenon by making the distribution of flow rate uniform in the unit even when resistance is adhered on the upstream side of the blower (PTL 1). The cross-flow blower disclosed in PTL 1 has a plurality of first blades each having an outer peripheral thickness greater than an inner peripheral thickness and a plurality of second blades each having an inner peripheral thickness greater than an outer peripheral thickness. The first blades and the second blades are disposed in order in the circumferential direction. When two first blades are in succession in the circumferential direction, the second blades are arranged on opposite sides of those first blades. When two second blades are in succession in the circumferential direction, the first blades are arranged on opposite sides of those second blades.
Japanese Patent Laying-Open No. 2006-170043 discloses a cross-flow fan aimed at reducing NZ noises while preventing reduction of air-blowing capacity and noise resulting from fluid oscillation (PTL 2). In the cross-flow fan disclosed in PTL 2, two or more kinds of blades having different shapes are arranged at random with a constant installation angle and installation pitch.
USPTO Backgrounds
USPTO Backgrounds