Abstract: A double-suction centrifugal fan includes: a first impeller coupled to a shaft; a second impeller provided with a second inlet port opened opposite to an electric motor and coupled to the shaft at a position farther from the electric motor than the first impeller; a first bell mouth connected to a first inlet port of the first impeller, and a second bell mouth connected to the second inlet port of the second impeller. An axial length L2 of the second bell mouth is greater than an axial length L1 of the first bell mouth.

Abstract: A double-suction centrifugal fan includes: a first impeller coupled to a shaft; a second impeller provided with a second inlet port opened opposite to an electric motor and coupled to the shaft at a position farther from the electric motor than the first impeller; a first bell mouth connected to a first inlet port of the first impeller, and a second bell mouth connected to the second inlet port of the second impeller. An axial length L2 of the second bell mouth is greater than an axial length L1 of the first bell mouth.

Abstract: An axial-flow fan includes a boss and a plurality of blades integrally resin-molded with a hub. An axial hole of the boss has a shaft of a drive motor inserted. The axial hole is formed at an axial center of the hub. The hub includes an outer perimeter cylinder and a lid. The outer perimeter cylinder has an opening formed at the axial center, and the blades are formed so as to project from the outer perimeter cylinder. The lid extends from the outer perimeter cylinder toward the boss so as to cover the opening of the outer perimeter cylinder. The lid connects the boss and the outer perimeter cylinder together. Reinforcing ribs are integrally resin-molded together with the hub and the boss on both axial-direction sides of the lid. The reinforcing ribs reinforce the connection between the hub and the boss.

Abstract: An axial-flow fan has a blade with a recessed part that is recessed toward a front edge formed in a rear edge of the blade. A rounded stress-relieving part is formed in a positive pressure surface side and a negative pressure surface side of a front-edge-side edge part of the recessed part as seen in a cross-sectional view of the blade.

Abstract: An axial-flow fan includes a boss and a plurality of blades integrally resin-molded with a hub. An axial hole of the boss has a shaft of a drive motor inserted. The axial hole is formed at an axial center of the hub. The hub includes an outer perimeter cylinder and a lid. The outer perimeter cylinder has an opening formed at the axial center, and the blades are formed so as to project from the outer perimeter cylinder. The lid extends from the outer perimeter cylinder toward the boss so as to cover the opening of the outer perimeter cylinder. The lid connects the boss and the outer perimeter cylinder together. Reinforcing ribs are integrally resin-molded together with the hub and the boss on both axial-direction sides of the lid. The reinforcing ribs reinforce the connection between the hub and the boss.

Abstract: An axial-flow fan has a blade with a recessed part that is recessed toward a front edge formed in a rear edge of the blade. A rounded stress-relieving part is formed in a positive pressure surface side and a negative pressure surface side of a front-edge-side edge part of the recessed part as seen in a cross-sectional view of the blade.

Abstract: An axial-flow fan includes a hub and a plurality of blades integrally resin-molded to the hub at a plurality of joints, The plurality of blades are formed so as to project from an outer perimeter edge of the hub. Each joint has at least one first blade thinned-out part formed so that at least one radial rib extending radially toward an outer perimeter side is formed.