Impeller for centrifugal fan and centrifugal fan

Abstract

There is provided an impeller for a centrifugal fan which rotates around an axis extending from one side to the other side. The impeller includes a main plate, a plurality of blades each having one side portion located at the one side and the other side portion located at the other side, the one side portion being connected to a first surface of the main plate, and a connecting ring which connects the other side portions of the blades. A first circumferential groove to which a first balance weight is attachable is formed in an outer circumferential portion of a second surface of the main plate facing toward the one side. A second circumferential groove to which a second balance weight is attachable is formed in the connecting ring. An annular raised portion is formed on the first surface at a portion corresponding to the first circumferential groove.

What is claimed is: 
     
         1 . An impeller for a centrifugal fan which rotates around an axis extending from one side to the other side, the impeller comprising:
 a main plate;   a plurality of blades each having one side portion located at the one side and the other side portion located at the other side, the one side portion being connected to a first surface of the main plate; and   a connecting ring configured to connect the other side portions of the plurality of blades,   wherein a first circumferential groove to which a first balance weight is attachable is formed in an outer circumferential portion on a second surface of the main plate, the second surface facing toward the one side;   a second circumferential groove to which a second balance weight is attachable is formed in the connecting ring; and   an annular raised portion is formed on the first surface of the main plate, at a location corresponding to the first circumferential groove.   
     
     
         2 . The impeller for the centrifugal fan according to  claim 1 , wherein the main plate has a cup-shaped hub section protruding toward the other side; and
 a shaft is fixed to the hub section.   
     
     
         3 . The impeller for the centrifugal fan according to  claim 1 , wherein the connecting ring is provided on an outer side of the plurality of blades in a radial direction of the impeller, and connects surfaces of the blades located on the outer side in the radial direction. 
     
     
         4 . The impeller for the centrifugal fan according to  claim 1 , wherein the second circumferential groove is formed on a surface of the connecting ring facing toward the other side. 
     
     
         5 . The impeller for the centrifugal fan according to  claim 1 , wherein the second circumferential groove is formed on an outer side of the plurality of blades in a radial direction of the impeller. 
     
     
         6 . The impeller for the centrifugal fan according to  claim 1 , wherein at least one of the first circumferential groove of the main plate and the second circumferential groove of the connecting ring has an inner circumferential wall portion and an outer circumferential wall portion;
 the inner circumferential wall portion is inclined relative to a radial direction of the impeller at an angle α;   the outer circumferential wall portion is inclined relative to the radial direction at an angle β; and   the angle α is smaller than the angle β.   
     
     
         7 . The impeller for the centrifugal fan according to  claim 1 , wherein an inner diameter of the connecting ring is greater than an outer diameter of the main plate. 
     
     
         8 . The impeller for the centrifugal fan according to  claim 1 , wherein a thickness of the raised portion in the main plate is same as or less than a thickness of the main plate. 
     
     
         9 . A centrifugal fan comprising the impeller according to  claim 1 . 
     
     
         10 . An impeller for a centrifugal fan, comprising:
 a disc-shaped main plate;   a plurality of blades arranged on a first surface of the main plate; and   a connecting ring connecting end portions of the blades located at a side farther from the main plate;   wherein a first circumferential groove is formed in an outer circumferential portion of a second surface of the main plate, the second surface being opposite to the first surface; and   a second circumferential groove is provided in the connecting ring.   
     
     
         11 . The impeller according to  claim 10 , wherein an annular raised portion is provided on and projecting from the first surface of the main plate; and
 the annular raised portion is provided at a back of the first circumferential groove.   
     
     
         12 . The impeller according to  claim 11 , wherein a thickness of the raised portion in the main plate is not larger than a thickness of the main plate. 
     
     
         13 . The impeller according to  claim 10 , wherein the plurality of blades are connected by the connecting ring on an outer circumference side of the main plate. 
     
     
         14 . The impeller according to  claim 10 , wherein the second circumferential groove is provided on the connecting ring on a surface located on a farther side from the first surface of the main plate. 
     
     
         15 . The impeller according to  claim 10 , wherein a partition wall is provided inside of at least one of the first and second circumferential grooves to partition at least one of the first and second circumferential grooves in the circumferential direction. 
     
     
         16 . The impeller according to  claim 10 , wherein at least one of the first circumferential groove and the second circumferential groove has an inner circumferential wall portion and an outer circumferential wall portion;
 the inner circumferential wall portion is inclined relative to a radial direction of the main plate at an angle α;   the outer circumferential wall portion is inclined relative to the radial direction at an angle β; and   the angle α is smaller than the angle β.