| 摘要 |
PROBLEM TO BE SOLVED: To provide a centrifugal multiblade forward fan having larger air capacities, higher efficiency and lower noise in comparison with a conventional one, in a small- sized fan to be used for cooling electronic equipment. SOLUTION: This multiblade forward fan is provided with an impeller having blades having their longitudinal sides pinched between a disc-shaped main plate and an annular side plate and approximately radially arranged at constant distances, and a casing for pivotally supporting the impeller and for blowing air in the circumferential direction. In the blades, main blades 1a so curved that their outer peripheral parts have recessed shapes and their inner peripheral parts have projecting shapes as seen from the front in the rotational direction of the impeller and intermediate blades 1b curved along the main blades 1a and having the inside diameters larger than those of the main blades are alternately arranged. The inside diameters of the main blade 1a and the intermediate blade 1b are gradually increased from the main plate side to the side plate side and have the same diameter at the side plate side. The inlet angleβ1 of the main blade 1a is 70 deg. or less, the outlet angleβ2 of the main blade 1a is 15 deg. or more, the ratio of the main blade inside diameter D1 to the main blade outside diameter D2 on the main plate side is 0.6 or less, and the front edge angleθ1 of the main blade is larger than the blade pitch angleθ2.
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