Cooling fan and heat dissipation device having the same

Abstract

A heat dissipation device includes a heat sink and a cooling fan. The heat sink includes a substrate and a plurality of fins. The cooling fan includes a fan housing defining an air inlet and an air outlet at two opposite sides thereof, and an impeller received in the fan housing and mounted to a supporting base provided at the air inlet. The air outlet is positioned adjacent to the heat sink. The impeller includes a hub, a plurality of main blades and auxiliary blades. The hub includes a top wall located at the air outlet and a sidewall extending from the top wall. The main blades extend radially and outwardly from the sidewall. The auxiliary blades located on the top wall extend from a center of the top wall towards an outer periphery of the top wall.

1 . A cooling fan, comprising:
 a fan housing defining an air inlet and an air outlet at two opposite sides along an axial direction of the fan housing, respectively;   an impeller being received in the fan housing and mounted to a supporting base provided at the air inlet, the impeller comprising:   a hub including a top wall being located at the air outlet and a sidewall extending downwardly from the top wall;   a plurality of main blades extending radially and outwardly from the sidewall; and   a plurality of auxiliary blades being located on the top wall extending from a center of the top wall to an outer periphery of the top wall.   
   
   
       2 . The cooling fan of  claim 1 , wherein the auxiliary blades extend upwardly and perpendicularly from the top wall of the hub. 
   
   
       3 . The cooling fan of  claim 1 , wherein the auxiliary blades extend radially and curvedly from the center of the top wall towards the outer periphery of the top wall. 
   
   
       4 . The cooling fan of  claim 1 , wherein the auxiliary blades extend radially and linearly from the center of the top wall towards the outer periphery of the top wall. 
   
   
       5 . The cooling fan of  claim 1 , wherein each auxiliary blade has an inner first end connected to the center of the top wall and an outer second end extending to the outer periphery of the top wall, and the first ends of the auxiliary blades are converged at the center of the top wall. 
   
   
       6 . The cooling fan of  claim 1 , wherein each auxiliary blade has an inner section with a varied height and an outer section with a constant height, and the height of the inner section is lower than that of the outer section, such that a concave is defined at the center of the top wall. 
   
   
       7 . The cooling fan of  claim 1 , wherein each of the auxiliary blades has an inner first end adjacent to the center of the top wall and an outer second end extending to the outer periphery of the top wall, and the first ends of the auxiliary blades are spaced from the center of the top wall of the hub and arranged on a circumference of an imaginary circle which is concentric with the outer periphery of the top wall. 
   
   
       8 . The cooling fan of  claim 1 , wherein the top wall of the hub is doom-shaped, and tapered from the outer periphery of the top wall towards the center of the top wall and forms a conical tip at the center of the top wall. 
   
   
       9 . The cooling fan of  claim 8 , wherein each auxiliary blade has an upper edge and the upper edges of the auxiliary blades are coplanar, such that a height of each auxiliary blade gradually increases from the center of the top wall towards the outer periphery of the top wall. 
   
   
       10 . The cooling fan of  claim 1 , wherein each main blade has an upper edge higher than the top wall of the hub. 
   
   
       11 . A heat dissipation device, comprising:
 a heat sink comprising a substrate and a plurality of fins being located on the substrate;   a cooling fan being attached to the heat sink, comprising:   a fan housing defining an air inlet and an air outlet at two opposite sides along an axial direction of the fan housing, respectively, the air outlet being located adjacent to the heat sink and the air inlet being located distant from the heat sink;   an impeller being received in the fan housing and mounted to a supporting base provided at the air inlet, the impeller comprising:   a hub including a top wall being located at the air outlet and a sidewall extending downwardly from the top wall towards the air inlet;   a plurality of main blades extending radially and outwardly from the sidewall; and   a plurality of auxiliary blades being located on the top wall extending from a center of the top wall to an outer periphery of the top wall.   
   
   
       12 . The heat dissipation device of  claim 11 , wherein the auxiliary blades extend upwardly and perpendicularly from the top wall of the hub. 
   
   
       13 . The heat dissipation device of  claim 11 , wherein the auxiliary blades extend radially and curvedly from the center of the top wall towards the outer periphery of the top wall. 
   
   
       14 . The heat dissipation device of  claim 11 , wherein the auxiliary blades extend radially and linearly from the center of the top wall towards the outer periphery of the top wall. 
   
   
       15 . The heat dissipation device of  claim 11 , wherein each auxiliary blade has an inner first end connected to the center of the top wall and an outer second end extending to the outer periphery of the top wall, and the first ends of the auxiliary blades are converged at the center of the top wall. 
   
   
       16 . The heat dissipation device of  claim 15 , wherein each auxiliary blade has an inner section with a varied height and an outer section with a constant height, and the height of the inner section is lower than that of the outer section, such that a concave is defined at the center of the top wall. 
   
   
       17 . The heat dissipation device of  claim 11 , wherein each of the auxiliary blades has an inner first end adjacent to the center of the top wall and an outer second end extending to the outer periphery of the top wall, and the first ends of the auxiliary blades are spaced from the center of the top wall of the hub and arranged on a circumference of an imaginary circle which is concentric with the outer periphery of the top wall. 
   
   
       18 . The heat dissipation device of  claim 11 , wherein the top wall of the hub is doom-shaped, and tapered from the outer periphery of the top wall towards the center of the top wall and forms a conical tip at the center of the top wall. 
   
   
       19 . The heat dissipation device of  claim 18 , wherein each auxiliary blade has an upper edge and the upper edges of the auxiliary blades are coplanar, such that a height of each auxiliary blade gradually increases from the center of the top wall towards the outer periphery of the top wall. 
   
   
       20 . The heat dissipation device of  claim 11 , wherein each main blade has an upper edge higher than the top wall of the hub.