Patent Application
20110127017
This application is related to a co-pending application entitled “FAN MODULE AND HEAT DISSIPATION DEVICE INCORPORATING THE SAME” (attorney docket number US 30707), assigned to the same assignee of this application and filed on the same date.
1. Technical Field
The disclosure generally relates to heat dissipation, and particularly to a heat dissipation device having an improved fan module.
2. Description of Related Art
A typical heat dissipation device includes a heat sink and a cooling fan arranged on the heat sink. Electronic components are usually attached to a central portion of the heat sink, the location at which heat generated by the electronic component is primarily concentrated. The cooling fan includes an impeller. The impeller includes a hub and a plurality of blades around the hub. During operation of the cooling fan, the impeller rotates and produces airflow towards the heat sink. However, due to blocked access to the hub of the impeller, only a small portion of the airflow reaches the central portion of the heat sink immediately under the hub, such that heat concentrated at the central portion of the heat sink cannot be efficiently dissipated.
What is needed, therefore, is a heat dissipation device and a fan module of the heat dissipation device which can overcome the described limitations.
Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Referring to
The heat sink 20 includes a substrate 21 and a plurality of fins 23 extending perpendicularly up from the substrate 21. The substrate 21 is attached to the electronic component 10 at a central portion of a bottom surface thereof. The fins 23 are parallel to and spaced from each other. An air channel 231 is defined between every two adjacent fins 23. The fins 23 includes a plurality of inner fins 234 at a central portion of the heat sink 10, and a plurality of outer fins 236 around the inner fins 234. The inner fins 234 each have a length less than that of the outer fins 236, and therefore a recess 232 is defined in the central portion of the heat sink 20 over the inner fins 234.
The fan module 30 includes a main fan 31 and an assist fan 33 located below the main fan 31. The main and assist fans 31, 33 are axial fans.
Referring to
The frame 311 is mounted on the outer fins 236 of the heat sink 20. The frame 311 is substantially rectangular and hollow. The frame 311 defines an air inlet 3111 at a top end thereof, and an air outlet 3112 at a bottom end thereof. A base 3113 is formed at a central portion of the bottom end of the frame 311. The base 3113 is connected to the frame 311 via a plurality of ribs (not labeled). The air outlet 3112 is defined between the ribs. A central tube 3114 extends perpendicularly up from a central portion of the base 3113.
The bearing system 313 is received in the central tube 3114 of the frame 311. The bearing system 313 includes a sleeve 3131 and a locking ring 3132 located below the sleeve 3131. The sleeve 3131 is hollow and cylindrical, and the locking ring 3132 is annular.
The stator 315 includes a circuit board 3151 and a coil assembly 3152 located on the circuit board 3151. The circuit board 3151 and the coil assembly 3152 are mounted around the central tube 3114 of the frame 311.
The rotor 317 is rotatably mounted around the coil assembly 3152 of the stator 315. The rotor 317 includes a hub 3171, a shaft 3172, a plurality of blades 3173, and a magnet 3174. The hub 3171 is semi-enclosed, and includes a top wall 3175 and a sidewall 3176 extending perpendicularly down from an outer periphery of the bottom wall 3175. A top end of the shaft 3172 is fixed at a central portion of the top wall 3175 of the hub 3171. A middle portion of the shaft 3172 is received in the sleeve 3131. A bottom end of the shaft 3172 defines an annular notch 3177 engaged with the locking ring 3132 to limit floating of the rotor 317. The rotor 317 with the shaft 3172 is rotatable with respect to the bearing system 313. The blades 3173 extend radially out from an outer circumferential surface of the sidewall 3176 of the hub 3171. The magnet 3174 is annular, and contacted with an inner circumferential surface of the sidewall 3176 of the hub 3171.
The assist fan 33 is located under the hub 3171 of the main fan 31, and received in the recess 232 of the heat sink 20. The assist fan 33 has an outer diameter less than that of the main fan 31. The assist fan 33 includes a frame 331, a bearing system 333, and a rotor 337.
The frame 331 of the assist fan 33 is mounted on the inner fins 234 of the heat sink 20. The frame 331 has an outer diameter less than that of the frame 311 of the main fan 31, and slightly larger than an outer diameter of the sidewall 3176 of the hub 3171 of the main fan 31. The frame 331 is also substantially rectangular and hollow. The frame 331 defines an air inlet 3311 at a top end thereof, and an air outlet 3312 at a bottom end thereof. A base 3313 is formed at a central portion of the bottom end of the frame 331. The base 3313 is connected to the frame 331 via a plurality of ribs (not labeled). The air outlet 3312 is defined between the ribs. A central tube 3314 extends perpendicularly up from a central portion of the base 3313.
The bearing system 333 is the same as the bearing system 313 of the main fan 31 except in dimensions. The bearing system 333 also includes a sleeve 3331 and a locking ring 3332 located below the sleeve 3331.
The rotor 337 is rotatably mounted around the central tube 3314 of the frame 331. The rotor 337 includes a hub 3371, a shaft 3372, and a plurality of blades 3373. The hub 3371 has an outer diameter much less than that of the hub 3171 of the main fan 31. The hub 3371 also includes a top wall 3375 and a sidewall 3376 extending perpendicularly down from an outer periphery of the top wall 3375. A top end of the shaft 3372 is fixed to a central portion of the top wall 3375 of the hub 3371. A middle portion of the shaft 3372 is received in the sleeve 3331. A bottom end of the shaft 3372 defines an annular notch 3377 engaged with the locking ring 3332 to limit floating of the rotor 337. The rotor 337 with the shaft 3372 is rotatable with respect to the bearing system 333. The blades 3373 extend radially out from an outer circumferential surface of the sidewall 3376 of the hub 3371. Inner sides of the blades 3373 of the assist fan 33 adjacent to the hub 3371 are located within a range of a radius of the hub 3171 of the main fan 31 along a radial direction of the rotor 317 of the main fan 31. Outer sides of the blades 3373 of the assist fan 33 away from the hub 3371 are located beyond the hub 3171 of the main fan 31 along the radial direction of the rotor 317 of the main fan 31. This ensures that airflow from the main fan 31 is capable to flow towards outer portions of the blades 3373 of the assist fan 33 beyond the hub 3171 of the main fan 31, and therefore pushes the rotor 337 of the assist fan 33 to rotate.
During operation, the rotor 317 of the main fan 31 of the fan module 30 rotates and thus produces airflow. A portion of the airflow from the main fan 31 flows towards the outer fins 236 of the heat sink 20 via the air outlet 3112 of the main fan 31, and then enters corresponding air passages 231 between the outer fins 236, thereby taking heat away. Another portion of the airflow from the main fan 31 flows towards the blades 3373 of the assist fan 33 via the air outlet 3112 of the main fan 31 and the air inlet 3311 of the assist fan 33, and therefore pushes the rotor 337 of the assist fan 33 to rotate to produce airflow. The airflow from the assist fan 33 flows towards the inner fins 234 of heat sink 20 via the air outlet 3312 of the assist fan 33, and then enters corresponding air passages 231 between the inner fins 234 of heat sink 20, thereby taking away the heat concentrated at the central portion of the heat sink 20.
In the present heat dissipation device, the assist fan 33 is located below the hub 3171 of the rotor 317 of the assist fan 31. The inner sides of the blades 3373 adjacent to the hub 3371 of the assist fan 33 are located within the range of the radius of the hub 3171 of the main fan 31 along the radial direction of the rotor 317 of the main fan 31. Outer sides of the blades 3373 away from the hub 3371 of the assist fan 33 are located beyond the hub 3171 of the main fan 31 along the radial direction of the rotor 317 of the main fan 31. The blades 3373 of the rotor 337 of the assist fan 33 are pushed to rotate by the airflow from the main fan 31, and therefore produce airflow towards the central portion of the heat sink 20. Thus, heat concentrated at the central portion of the heat sink 20 can be efficiently dissipated by the assist fan 33. This prevents the electronic component 10 at the central portion of the substrate 21 of the heat sink 20 from overheating. In addition, the blades 3373 of the rotor 337 of the assist fan 33 are pushed to rotate by the airflow from the main fan 31. Therefore, a stator and a magnet are not required in the assist fan 33. The hub 3371 of the assist fan 33 is reasonably smaller than the hub 3171 of the main fan 31, and a blocked access to the hub 3371 of the assist fan 33 is relatively smaller. Thus, an airflow dead area under the hub 3171 of the main fan 31 is reduced, and the heat dissipation efficiency of the heat dissipation device is improved.
Referring to
In this embodiment, there is no frame in an assist fan 33a of the fan module 30a. A bearing system 333a of the assist fan 33a is received in a hub 3371a of a rotor 337a of the assist fan 33a, with a sleeve 3331a of the bearing system 333a of the assist fan 33a fixed to an inner circumferential surface of the hub 3371a of the rotor 337a of the assist fan 33a. A shaft 3372a of the assist fan 33a is coaxial to the shaft 3172 of the main fan 31. A top end of the shaft 3372a of the assist fan 33a is fixed at a central portion of a bottom surface of the base 3113 of the main fan 31. A middle portion of the shaft 3372a is received in the sleeve 3331a of the bearing system 333a. A bottom end of the shaft 3372a defines an annular notch 3377a engaged with a locking ring 3132a of the bearing system 333a, and thus the hub 3371a of the assist fan 33a is rotatable with respect to the shaft 3372a. During operation, a portion of the airflow form the main fan 31 flows towards the blades 3373a of the assist fan 33a, and pushes the rotor 337a and the bearing system 333a of the assist fan 33a to rotate around the shaft 3372a, thereby producing airflow towards the central portion of the heat sink 20.
In the present fan module 30a, the frame is omitted, and thus, a size of the hub 3371a of the assist fan 33a in this embodiment can be further reduced relative to the first embodiment, and therefore a blocked access to the hub 3371a of the assist fan 33a is relatively smaller. Thus, the airflow dead area under the hub 3171 of the main fan 31 is reduced, and the heat dissipation efficiency of the heat dissipation device is further improved.
It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 98141252 | Dec 2009 | TW | national |
