Centrifugal fan

Abstract

A centrifugal fan includes: a motor; an impeller having an inlet port, the impeller being configured to be rotated by the motor and to discharge air suctioned from the inlet port outward from an outer circumferential portion of the impeller; a lower casing that is located below the impeller; a circuit board disposed between the lower casing and the impeller, the circuit board being, mounted with an electrical component including a drive circuit that drives the motor, wherein the impeller has a recessed portion formed in an annular shape around a rotational axis and on a lower face that faces the lower casing and the circuit hoard, and wherein at least a part of the electrical component is located inside the recessed portion of the impeller.

What is claimed is: 
     
         1 . A centrifiigal fan comprising:
 a motor;   an impeller having an inlet port, the impeller being configured to be rotated by the motor and to discharge air suctioned from the inlet port outward from an outer circumferential portion of the impeller;   a lower casing that is located below the impeller;   a circuit board disposed between the lower casing and the impeller, the circuit board being mounted with an electrical component including a drive circuit that drives the motor,   wherein the impeller has a recessed portion formed in an annular shape around a rotational axis and on a lower face that faces the lower casing and the circuit board, and   wherein at least a part of the electrical component is located inside the recessed portion of the impeller.   
     
     
         2 . The centrifugal fan according to  claim 1 ,
 wherein the lower casing is provided with an accommodating portion that is formed to concave downward, and   wherein at least a part of the motor and at least a part of the circuit board are located inside the accommodating portion of the lower casing.   
     
     
         3 . The centrifugal fan according to  claim 1 ,
 wherein the impeller has a hub connected to the motor, a main plate connected to the hub, an annular shroud, and a plurality of blades arranged between the main plate and the shroud, and   wherein the recessed portion is formed on a lower face of the main plate that faces the lower casing and the circuit board.   
     
     
         4 . The centrifugal fan according to  claim 3 ,
 wherein the impeller has a diameter that is greater than a diameter of a circle passing through an outermost circumferential edge of the blades, and   wherein a gap size between the shroud and the main plate in an axial direction gradually is set to be enlarged from a position of the outermost circumferential edge of the blades toward an outer circumferential edge of the impeller.   
     
     
         5 . The centrifugal fan according to  claim 4 ,
 wherein a part of one of a lower face of the of the shroud and an upper face of the main plate at the outer circumferential edge of the impeller is curved to form a wing upper surface shape.   
     
     
         6 . The centrifugal fan according to  claim 4 ,
 wherein an upper face of the main plate at the outer circumferential edge of the impeller is curved.