Centrifugal Fan and Air Conditioner Using the Same

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.

1 . A centrifugal fan including a hub for fixing a rotary shaft of a motor, a main plate formed on an outer circumference of the hub, a shroud disposed to be opposed to the main plate, which shroud forms an air passage, a plurality of impellers disposed between the main plate and the shroud, and a bellmouth disposed at a suction side of the shroud, the centrifugal being characterized in that a plurality of projections or recesses are formed on a surface of the shroud facing the bellmouth, the projections or recesses forming air streams flowing from a center of the shroud toward an outer circumference of the shroud along the surface when the fan is operated. 
   
   
       2 . The centrifugal fan according to  claim 1 , characterized in that a plurality of rib-shaped projections are formed on the surface of the shroud facing the bellmouth, which rib-shaped projections form air streams flowing from the center of the shroud toward the outer circumference of the shroud along the surface when the fan is operated. 
   
   
       3 . The centrifugal fan according to  claim 2 , characterized in that the rib-shaped projections on the surface of the shroud facing the bellmouth have substantially the same inclination as that of the camber line of the shroud side blade element of the impellers, and are formed at even intervals on the entire circumference of the surface of the shroud facing the bellmouth. 
   
   
       4 . The centrifugal fan according to  claim 3 , characterized in that the pitch of the rib-shaped projections on the surface of the shroud facing the bellmouth is smaller than the pitch of the impellers. 
   
   
       5 . The centrifugal fan according to  claim 4 , characterized in that the height of the rib-shaped projections on the surface of the shroud facing the bellmouth is equivalent to the thickness of a plate that forms the shroud. 
   
   
       6 . The centrifugal fan according to  claim 2 , characterized in that each of the rib-shaped projections on the surface of the shroud facing the bellmouth includes a front side, a rear side, and a distal end face, wherein the front side vertically extends from the surface of the shroud facing the bellmouth and is located forward in the rotation direction of an impeller wheel, wherein the rear side vertically extends from the surface of the shroud facing the bellmouth and is located rearward in the rotation direction of the impeller wheel, wherein the distal end face connects the front side and the rear side with each other, and wherein the distal end face and the front side are coupled to each other so as to be substantially orthogonal to each other, and the rear side is curved to the front side toward the distal end face. 
   
   
       7 . An air conditioner characterized by the centrifugal fan according to  claim 1  mounted therein. 
   
   
       8 . The air conditioner according to  claim 7 , characterized in that an air suction port that draws in indoor air is formed at the front side of the fan suction port of the centrifugal fan, a heat exchanger is disposed at the blow-out side of the centrifugal fan, and an air blow-out port that blows out air indoors is disposed downstream of the heat exchanger. 
   
   
       9 . The air conditioner according to  claim 7 , characterized in that the centrifugal fan is a turbo fan.