Cooling Fan Having a Radial-Air-Gap Motor and a Method for Determining the Dimensional Proportion of the Motor

Abstract

A cooling fan having a radial-air-gap motor is disclosed. The cooling fan includes a fan frame, an impeller and a stator assembly. The fan frame has a shaft-coupling portion. The impeller has a hub, a shaft and a plurality of blades. The blades are arranged on an outer periphery of the hub. At least one magnetic element is arranged on an inner periphery of the hub. There is a height between a bottom face of the shaft-coupling portion and a top face of the hub. There is a maximum thickness between the bottommost and uppermost faces of the magnetic plate unit. A ratio of the maximum thickness to the height is between 0.1 and 0.6. A method for determining the dimensional proportion of the motor is also disclosed. The method selects a ratio of a maximum thickness to a height as 0.1 to 0.6.

What is claimed is: 
     
         1 . A cooling fan having a radial-air-gap motor, comprising:
 a fan frame having a shaft-coupling portion;   an impeller having a hub, a shaft and a plurality of blades, wherein the shaft is connected to the hub and rotatably coupled with the shaft-coupling portion of the fan frame, wherein the plurality of blades is annularly arranged on an outer periphery of the hub, and wherein at least one magnetic element is arranged on an inner periphery of the hub; and   a stator assembly having a magnetic plate unit, wherein the magnetic plate unit has a face facing and spaced from the at least one magnetic element by the radial air gap,   wherein there is a height (A) between a bottom face of the shaft-coupling portion of the fan frame and a top face of the hub of the impeller along an axial direction, wherein the height (A) is between 2 mm and 4.5 mm, wherein there is a maximum thickness (B) between the bottommost and uppermost faces of the magnetic plate unit along the axial direction, and wherein a ratio of the maximum thickness (B) to the height (A) is between 0.1 and 0.6.   
     
     
         2 . The cooling fan having the radial-air-gap motor as claimed in  claim 1 , wherein the ratio of the maximum thickness (B) to the height (A) is between 0.2 and 0.4. 
     
     
         3 . The cooling fan having the radial-air-gap motor as claimed in  claim 1 , wherein the magnetic plate unit includes at least one magnetic plate. 
     
     
         4 . The cooling fan having the radial-air-gap motor as claimed in  claim 3 , wherein the magnetic plate unit includes a plurality of magnetic plates, and wherein the maximum thickness (B) is a distance between a bottom face of the bottommost magnetic plate and a top face of the uppermost magnetic plate of the magnetic plate unit along the axial direction. 
     
     
         5 . The cooling fan having the radial-air-gap motor as claimed in  claim 1 , wherein the at least one magnetic element has a height along the axial direction smaller than or equal to a thickness of the magnetic plate unit along the axial direction. 
     
     
         6 . The cooling fan having the radial-air-gap motor as claimed in  claim 5 , wherein the magnetic element includes an outer circumferential face having a first central portion along the axial direction, wherein the magnetic plate unit includes an inner circumferential face having a second central portion along the axial direction, and wherein the first and second central portions are aligned with each other in a radial direction. 
     
     
         7 . A method for determining the dimensional proportion of a motor of a cooling fan that has a radial air gap, comprising:
 selecting a ratio of a maximum thickness (B) of the motor to a height (A) of the motor as 0.1 to 0.6, wherein the maximum thickness (B) is a maximum distance between the bottommost and uppermost faces of a magnetic plate unit of the motor along an axial direction, and wherein the height (A) is a distance between a bottom face of a shaft-coupling portion of a fan frame of the motor and a top face of a hub of an impeller of the motor along the axial direction;   determining the value of one of the height (A) and the maximum thickness (B); and   determining the value of the other one of the height (A) and the maximum thickness (B) based on the range of the ratio (B/A) and the previously determined value, wherein the height (A) is between 2 mm and 4.5 mm.   
     
     
         8 . The method for determining the dimensional proportion of the motor of the cooling fan as claimed in  claim 7 , wherein the range of the ratio (B/A) is 0.2 to 0.4.