Heat dissipation device and fan module thereof

Abstract

An exemplary fan module includes a main fan and an assist fan. The main and assist fans each include a rotor which includes a hub and a plurality of blades around the hub. The assist fan is located below the hub of the main fan. Inner sides of the blades of the assist fan adjacent to the hub of the assist fan are located within a range of a radius of the hub of the main fan along a radial direction of the rotor of the main fan. Outer sides of the blades of the assist fan away from the hub of the assist fan are located beyond the hub of the main fan along the radial direction of the rotor of the main fan. The blades of the assist fan are pushed to rotate by airflow from the main fan to produce airflow towards a heat sink.

1 . A fan module, comprising:
 a main fan comprising a rotor, the rotor of the main fan comprising a hub and a plurality of blades around the hub; and   an assist fan located below the hub of the main fan, the assist fan comprising a rotor, the rotor of the assist fan comprising a hub and a plurality of blades around the hub, inner sides of the blades of the assist fan adjacent to the hub of the assist fan being located within a range of a radius of the hub of the main fan along a radial direction of the rotor of the main fan, outer sides of the blades of the assist fan away from the hub of the assist fan being located beyond the hub of the main fan along the radial direction of the rotor of the main fan, the blades of the assist fan pushed to rotate by airflow from the main fan to produce airflow.   
     
     
         2 . The fan module of  claim 1 , wherein the assist fan further comprises a bearing system and a shaft, the bearing system of the assist fan fixed in the hub of the rotor of the assist fan, a top end of the shaft of the assist fan fixed on the main fan, the rotor and the bearing system of the assist fan being rotatable with respect to the shaft of the assist fan. 
     
     
         3 . The fan module of  claim 2 , wherein the main fan further comprises a base supporting the rotor of the main fan, the top end of the shaft of the assist fan fixed on the base of the main fan. 
     
     
         4 . The fan module of  claim 2 , wherein the bearing system of the assist fan comprises a sleeve and a locking ring located below the sleeve, the sleeve fixed on an inner circumferential surface of the hub of the rotor of the assist fan, a middle portion of the shaft of the assist fan received in the sleeve, a bottom end of the shaft of the assist fan defining a notch engaged with the locking ring of the bearing system of the assist fan. 
     
     
         5 . The fan module of  claim 1 , wherein the assist fan further comprises a base and a bearing system, a central tube extending upwardly from the base of the assist fan, the bearing system of the assistant fan received in the central tube of the assistant fan, the rotor of the assist fan further comprising a shaft with a top end fixed on the hub of the rotor of the assist fan, and a bottom end rotatably mounted in the bearing system. 
     
     
         6 . The fan module of  claim 5 , wherein the hub of the rotor of the assist fan is disposed around the central tube. 
     
     
         7 . The fan module of  claim 5 , wherein the bearing system of the assist fan comprises a sleeve and a locking ring located below the sleeve, a middle portion of the shaft of the assist fan received in the sleeve, a bottom end of the shaft of the assist fan defining a notch engaged with the locking ring of the bearing system of the assist fan. 
     
     
         8 . The fan module of  claim 1 , wherein the main fan defines an air outlet at a bottom end thereof, airflow from the main fan flowing towards the blades of the rotor of the assist fan via the air outlet of the main fan. 
     
     
         9 . The fan module of  claim 1 , wherein the assist fan has an outer diameter less than that of the main fan. 
     
     
         10 . A heat dissipation device, comprising:
 a heat sink; and   a fan module arranged on the heat sink, the fan module comprising:
 a main fan comprising a rotor, the rotor of the main fan comprising a hub and a plurality of blades around the hub; and 
 an assist fan located below the hub of the main fan, the assist fan comprising a rotor, the rotor of the assist fan comprising a hub and a plurality of blades around the hub, inner sides of the blades of the assist fan adjacent to the hub of the assist fan being located within a range of a radius of the hub of the main fan along a radial direction of the rotor of the main fan, outer sides of the blades of the assist fan away from the hub of the assist fan being located beyond the hub of the main fan along the radial direction of the rotor of the main fan, the blades of the assist fan pushed to rotate by airflow from the main fan to produce airflow. 
   
     
     
         11 . The heat dissipation device of  claim 10 , wherein the heat sink defines a recess in a central portion thereof, the assist fan of the fan module received in the recess. 
     
     
         12 . The heat dissipation device of  claim 10 , wherein the assist fan further comprises a bearing system and a shaft, the bearing system of the assist fan fixed in the hub of the rotor of the assist fan, a top end of the shaft of the assist fan fixed on the main fan, the rotor and the bearing system of the assist fan being rotatable with respect to the shaft of the assist fan. 
     
     
         13 . The heat dissipation device of  claim 12 , wherein the main fan further comprises a base supporting the rotor of the main fan, the top end of the shaft of the assist fan fixed on the base of the main fan. 
     
     
         14 . The heat dissipation device of  claim 12 , wherein the bearing system of the assist fan comprises a sleeve and a locking ring located below the sleeve, the sleeve fixed on an inner circumferential surface of the hub of the rotor of the assist fan, a middle portion of the shaft of the assist fan received in the sleeve, a bottom end of the shaft of the assist fan defining a notch engaged with the locking ring of the bearing system of the assist fan. 
     
     
         15 . The heat dissipation device of  claim 10 , wherein the assist fan further comprises a base and a bearing system, a central tube extending upwardly from the base of the assist fan, the bearing system of the assistant fan received in the central tube of the assistant fan, the rotor of the assist fan further comprising a shaft with a top end fixed on the hub of the rotor of the assist fan, and a bottom end rotatably mounted in the bearing system. 
     
     
         16 . The fan module of  claim 15 , wherein the hub of the rotor of the assist fan is disposed around the central tube. 
     
     
         17 . The fan module of  claim 15 , wherein the bearing system of the assist fan comprises a sleeve and a locking ring located below the sleeve, a middle portion of the shaft of the assist fan received in the sleeve, a bottom end of the shaft of the assist fan defining a notch engaged with the locking ring of the bearing system of the assist fan. 
     
     
         18 . The fan module of  claim 10 , wherein the assist fan has an outer diameter less than that of the main fan.