1. Technical Field
The disclosure generally relates to centrifugal fans and, more particularly, to an electronic device incorporating a centrifugal fan for dissipating heat generated therefrom.
2. Description of Related Art
With the fast development of the electronics industry, electronic components, such as central processing units (CPUs), or video graphics array (VGA) chips, are being made with ever faster operating speeds. During operation of the electronic components, a large amount of heat is generated. Greater emphasis is now being laid on increasing the efficiency and effectiveness of heat dissipation devices so as to keep operational temperature of the electronic components within a suitable range.
Conventionally, a fan is used in combination with a heat dissipation device to produce an airflow in order to remove heat from the electronic components. Since most of electronic systems that contain electronic components therein, such as a laptop computer or a desktop computer, do not have enough space therein, a centrifugal fan which requires only a small space for installation is generally used. The centrifugal fan has at least an air inlet and an air outlet oriented perpendicularly to the at least an air inlet. In use, the centrifugal fan generates an airflow from the at least an air inlet towards the electronic component via the air outlet, thus cooling the electronic component continuously.
The diameter of the at least an air inlet is smaller than the diameter of an impeller of the centrifugal fan. For avoiding friction between the impeller and a housing of the centrifugal fan, an axial clearance must be defined between the housing and the impeller, which conflicts with the requirement that the centrifugal fan can only occupy a small space in the electronic system. Additionally, due to the presence of the clearance, portion of the airflow flows back to the at least an air inlet via the clearance directly, thus to cause air turbulence at the least an air inlet and decrease air pressure in the centrifugal fan.
Therefore, there is a need for a centrifugal fan, which can eliminate the limitations described.
Reference will now be made to the drawing figures to describe the embodiment in detail.
Referring to
The housing 11 includes a base plate 111, a volute side plate 112 extending upwardly and perpendicularly from an outer periphery of the base plate 111. The base plate 111 and the side plate 112 are integrally formed by injection molding process as a single piece. The base plate 111 and the side plate 112 cooperatively define a space for receiving the impeller 12 therein. The side plate 112 surrounds the impeller 12. A volute air channel 14 is defined between the side plate 112 and an outer periphery of the impeller 12.
Referring to
Referring to
Each of the blades 121 is planar-shaped and extends outwardly from the annular wall 1202 of the hub 120 along a clockwise direction, as viewed from
Each of the first blade portions 1211 has a top face and an opposite bottom face. The top face of the first blade portion 1211 extends horizontally along an extension direction of the first blade portion 1211, and the bottom face of the first blade portion 1211 extends downwardly along the extension direction of the first blade portion 1211. Thus, a longitudinal height of the first blade portion 1211 gradually increasing as the first blade portion 1211 extends outwardly from the hub 120 towards the second blade portion 1212. The bottom face of the first blade portion 1211 at the distal end is lower than the bottom face of the first blade portion 1211 at an inner end fixed to the annular wall 1202. An outer diameter of the first blade portion 1211 substantially equals to the diameter of the air inlet 114. Each of the second blade portions 1212 has a top face and an opposite bottom face. The top face and the bottom face of the second blade portion 1212 are horizontally and parallel to the bottom wall 1130. The longitudinal height of each of the second blade portions 1212 is constant. The top face of the second blade portion 1212 is coplanar with the top face of the first blade portion 1211, and the bottom face of the first blade portion 1211 at the inner end is higher than the bottom face of the second blade portion 1212. The longitudinal height of second blade portions 1212 equals to a maximal longitudinal height of the first blade portions 1211. An inner diameter of the second blade portions 1212 is substantially the same as that the diameter of the air inlet 114.
For avoiding contact and friction between the impeller 12 and the housing 11 as the impeller 12 rotates, a radial clearance is defined between distal ends of the second blade portions 1212 and the side wall 1131 of the concave portion 113, and an axial clearance is defined between the bottom faces of the second blade portions 1212 and the bottom wall 1130 of the concave portion 113. In the present embodiment, an outer diameter of the second blade portions 1212 is slightly smaller than the diameter of the concave portion 113, and the radial clearance of is about 0.05 mm. The bottom faces of the second blade portions 1212 are lower than the base plate 111 of the housing 11, thus a size of the blade 121 at the second blade portion 1212 is increased. A windward lateral surface of each of the blades 121 is thus increased for increasing air pressure and amount of airflow during operation of the centrifugal fan 10.
Alternatively, the supporting plate 1150 of the base 115 and the bottom wall 1130 of the concave portion 113 can be coplanar, and thus the supporting plate 1150 is lower than the base plate 111 of the housing 11. Accordingly, the ribs 1150 extend horizontally form the outer periphery of the supporting plate 1150 to the inner periphery of the bottom wall 1130. The longitudinal height of the first blade portion 1511 of each of the blades 121 above the base 115 can be increased to equal the longitudinal height of the second blade portion 1212. That is, the windward lateral surface of each of the blades 121 is further increased for increasing the air pressure and amount of airflow during operation of the centrifugal fan 10.
Referring to
During operation, high-pressure airflow generated by the rotation of the blades 121 accumulates in the air channel 14 and flows towards the air outlet 118 along the side plate 112 of the housing 11. Due to the concave portion 113, a longitudinal height of the space above the concave portion 113 for receiving the blades 121 is increased; thus, the longitudinal height of the second blade portion 1212 of each of the blades 121 can be increased for increasing air pressure and amount of airflow during operation of the centrifugal fan 10. Moreover, since the second blade portions 1212 are lower than the base plate 111 of the housing 11, the axial clearance and the air channel 14 are staggered up and down, refluxed airflow around an outer periphery of the blades 121 towards the air inlet 114 is blocked by the distal ends of the second blade portions 1212. As a result, air turbulence at the air inlet 114 caused by the refluxed airflow is reduced so that exterior air enters into the centrifugal fan 10 more smoothly, noise generated by the air turbulence is reduced and air pressure and amount of airflow in the centrifugal fan 10 is further increased.
Referring to
It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.