Centrifugal fan

Abstract

In a centrifugal fan, an impeller portion, fitted to a rotor portion which rotates with respect to a stator portion, rotates around a central axis J 1 . The impeller portion is housed in a housing comprised of a housing body and a cover portion. By rotation of the impeller portion, air is taken in from an inlet and delivered from an outlet. In the centrifugal fan, an annular protrusion, protruding toward a connection plate on the lower side of blades, is formed in the base portion in order to make a space between the impeller portion and the base portion small. A depression for partially expanding a space between the connection plate and the base portion is provided in the annular protrusion.

1 . A centrifugal fan, comprising: 
 a substantially bottomed cylindrical cup portion, including a cylindrical yoke portion with a prescribed central axis as the center;    a field magnet, arranged inside the cup portion and fixed to the cup portion;    an impeller portion, connected to the cup portion, having a plurality of blades arranged around the central axis outside the cup portion, and rotated along with the cup portion to take in air from the bottom side of the cup portion and discharge the air in a direction separating from the central axis;    a housing, having a side wall portions which covers the periphery of the impeller portion and has a pair of ends in a circumferential direction, a base portion which covers the opening side of the cup portion and a cover portion in which an inlet opposed to the bottom of the cup portion is formed, the housing being where a width of a flow channel between the side wall portion and the impeller portion gradually expands toward an outlet as an opening between the pair of ends;    a bearing mechanism, which rotatably supports the cup portion with the central axis as the center with respect to the base portion; and    an armature, which is fixed to the base portion and at least partially located inside the cup portion, and generates a torque with the central axis as the center between the located position and the field magnet, wherein    the base-portion-side end of the impeller portion is circular or annular, and its central axis agrees with the central axis,    a depression locally depressed in the direction separating from the impeller portion along the circumferential direction is formed in the base portion, and    a space between the end and the base portion expands in the depression, and is substantially constant in other portions.    
   
   
       2 . The centrifugal fan according to  claim 1 , wherein 
 the impeller portion includes a connection plate for connecting the plurality of blades at the base-portion-side portions of blades, and    the connection plate constitutes the base-portion-side end of the impeller portion.    
   
   
       3 . The centrifugal fan according to  claim 2 , wherein 
 the connection plate is an annular plate having a width in a radial direction, and    the inner edge of the annular plate in the radial direction is located on the peripheral surface or the inside of the cup portion.    
   
   
       4 . The centrifugal fan according to  claim 1 , 
 wherein the plurality of blades radiate from the outside surface of the cup portion.    
   
   
       5 . The centrifugal fan according to  claim 1 , 
 wherein the depression spreads in the circumferential direction in the range between not smaller than 30 degrees and not larger than 180 degrees with the central axis as the center, and    the end of the depression on the downstream side in a rotational direction of the impeller portion is located on the upstream side of the downstream-side end out of the pair of ends of the side wall.    
   
   
       6 . The centrifugal fan according to  claim 5 , 
 wherein the base portion includes another depression for expanding the space between the base-portion-side end of the impeller portion and the base portion.    
   
   
       7 . The centrifugal fan according to  claim 1 , 
 wherein the base portion includes an arc-shaped protrusion protruding toward the base-portion-side end of the impeller portion, and between the ends of the arc-shaped protrusion, a space formed with a bottom of the impeller portion expands to give the depression.    
   
   
       8 . The centrifugal fan according to  claim 1 , further comprising, between the armature and the base portion, a circuit board on which an electronic component for controlling a current to be supplied to the armature is mounted, wherein 
 the position of the electronic component in an axial direction substantially agrees with the position of the depression in the axial direction.    
   
   
       9 . The centrifugal fan according to  claim 5 , 
 wherein the base portion includes an arc-shaped protrusion protruding toward the base-portion-side end of the impeller portion, and between the ends of the arc-shaped protrusion, a space formed with the bottom of the impeller portion expands to give the depression.