Patent Publication Number: US-8113793-B2

Title: Fan

Description:
BACKGROUND OF THE INVENTION 
     The Non-provisional applications claims priority under 35 U.S.C §119(a) on Patent Application No(s). 097103928, filed in Taiwan, Republic of China on Feb. 1, 2008, the entire contents of which are hereby incorporated by references. 
     FIELD OF THE INVENTION 
     The present invention relates to a fan and a motor thereof, and in particular to a fan having a motor capable of decreasing weight of the rotor and rotating inertia, and reducing size of the hub so as to increase the volume of the flow path. 
     DESCRIPTION OF THE RELATED ART 
     Nowadays, many apparatuses (such as fans) utilize motors to facilitate operation. Therefore, the quality of motors is also a key point in the quality of the apparatuses. In order to be competitive, the motor applied to the fan or other relative products needs to be designed with additional considerations to increase heat dissipating efficiency, to reduce vibration and noises and so on. If the above requirements are not achieved, noises will be produced, and the life span of the applied product will be reduced. 
     Referring to  FIG. 1 , a sectional view of a conventional axial fan is shown. The axial fan  1  is designed to have an outrunner motor. The axial fan  1  has an impeller consisting of a hub  13  and a plurality of blades  14  connected with the hub  13 . The impeller is driven by the motor. The motor includes a stator  11  and a rotor. The rotor consists of a metal casing  15 , a magnetic band  16  and a shaft  17 . To operate the axial fan  1 , the magnetic band  16  is disposed on an inner side of the metal casing  15 , such that when the axial fan  1  is electrified, the stator  11  generating magnetic force pushes the magnetic band  16  and drives the impeller to rotate. 
     However, during the rotation of the impeller, rotating inertia is generated due to the shape of the motor, causing the axial fan  1  to vibrate during its operation. Thus, noises are produced and application in products requiring high stability is hindered. 
     Moreover, disposition of the metal casing  15  and the magnetic band  16  on the inner side of the hub  13  results in an increased-size hub  13 . The hub  13  takes position in the airflow passage, narrowing the airflow passage of the fan and further reducing the heat dissipation efficiency thereof. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides a fan and a motor thereof to widen the airflow passage, increase heat dissipation efficiency, decrease rotating inertia, lower the noise, and extend the life span and raise the stability of the product. 
     Accordingly, the fan includes a fan frame, a rotor and a stator. The fan frame includes a base. The rotor includes a hub, a bushing and a magnetic member, wherein the magnetic member sleeves on the bushing. The stator, disposed on the base and coupled with the rotor, includes a shaft through the bushing, wherein an end of the shaft is fixed on the base. 
     The base includes a bottom wall, and a predetermined distance is kept between the bottom wall and an air outlet of the fan frame. The base further includes a side wall surrounding a periphery of the bottom wall to define a first accommodating space and a second accommodating space. A cross-section of the base along an axial direction forms an H-shaped structure. The fan further includes a circuit board received in the first accommodating space. The stator is received in the second accommodating space. The bottom wall includes a protrusion extended from the bottom wall toward the air outlet of the fan to connect with the circuit board. Otherwise, a fastening structure is utilized to abut the circuit board in the first accommodating space. 
     Preferably, the end of the shaft is embedded in the protrusion, and an other end of the shaft includes a groove for a fastener to be engaged. 
     A plurality of ribs are formed between the base and an exterior wall of the fan frame, and the connector extends upwardly. A plurality of blades are formed around the hub and extends upwardly. Preferably, bottom peripheries of the blades extend axially toward the air outlet of the fan and exceed a top periphery of the side wall of the base. 
     The magnetic member is a permanent magnet, and the bushing includes metal. 
     The fan further includes at least one bearing disposed in the bushing. A periphery is formed on center of a top surface of the hub to define a recess, and the shaft is received in the recess. 
     The stator further includes at least one silicon steel wound by coils or a bobbin wound by coils, all of which are disposed around the magnetic member. Otherwise, the stator further includes a coil and a metal casing covering the coil, wherein the coil is fixed on a rack. The fan is an axial fan. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a sectional view of a conventional axial fan; 
         FIG. 2  is a schematic view of a fan according to a first embodiment of the present invention; and 
         FIG. 3  is a schematic view of a fan according to a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
     Referring to  FIG. 2 , a schematic view of a fan according to a first embodiment of the present invention is shown. The fan  2  includes a fan frame  20 , a stator  30  and a rotor  30 . The fan frame  20  includes a base  21 , and the stator  31  is placed on the base  21 . The stator  30  has a shaft  23  disposed on the base  21 , wherein one end of the shaft  23  is embedded or covered in the base  21 , and extends toward an air inlet of the fan  2 . Additionally, the other end of the shaft  23  has a groove  231  for engaging with a fastener “C”. 
     The stator  30  includes at least one silicon steel or a bobbin wound by coils, all of which are disposed around the magnetic member. The rotor  40  includes a hub  41 , a bushing  43  and a plurality of blades  42 . A protruding periphery is formed on the center of a top surface of the hub  41  to define a recess  411 . The bushing  43  is made by metal and the bushing  43  is connected with the recess  411 . There is at least one bearing  431  disposed in the bushing  43 , and there is further a magnetic member  44 , such as a permanent magnet, disposed outside the bushing  43 . When the fan  2  is in operation, the shaft  23  moves relate to the bushing  43 , the bearing  431  and the magnetic member  44  of the rotor  40 . 
     The base  21  includes a bottom wall  211  and a side wall  212 . The side wall  212  surrounds a periphery of the bottom  211 , and a predetermined distance “h” is kept between the bottom wall  211  and an air outlet of the fan frame  20 , so that a cross-section of the base  21  along an axial direction forms an H-shaped structure. The bottom wall  211  is presented as a demarcation. The portion below the bottom wall  211  is defined as a first accommodating space  213 , and the portion above the bottom wall  211  is defined as a second accommodating space  214 . The first accommodating space  213  receives a circuit board  25 , and the second accommodating space  214  receives the stator  30 . The stator  30  is electrically coupled to the circuit board  25  to be driven. 
     The bottom wall  211  includes a protrusion  211   a  which extends from the bottom wall  211  toward the air outlet of the fan frame  20 . The end of the shaft  23  is embedded in the protrusion  211   a  to intensify the connection between the shaft  23  and the bottom wall  211 . The circuit board  25  is received in the first accommodating space  213  and the circuit board  25  has a center opening for allowing the circuit board  25  to be fixed on the periphery of the protrusion  211   a.    
     During assembly, the end of the shaft  23  penetrates through the bearing  431  with the bushing  43  and is fixed on the base. A fastener “C”, such as a C-shaped ring, engages with a groove  231  on the other end of the shaft  23  at the air inlet of the fan  2 . The outer perimeter of the fastener “C” is slightly greater than the outer perimeter of the shaft  23 , such that the bearing  431  within the bushing  43  is blocked by the fastener “C”, preventing the shaft  23  from shifting axially in order to limit the movement of the shaft. The above design provides a fan  2  with easy assembly and disassembly. During operation, heats generated by the fan  2  are able to be dissipated through the recess  411  of the hub  41 , extending the life span of the fan  2 . 
     In the embodiment, because the magnetic member  44  of the fan  2  is disposed outside of the bushing  43 , the weight of entire rotor  40  is centralized, and the diameter of the hub is accordingly decreased. Therefore, rotating inertia is substantially decreased, the vibration is reduced, and the noise is restrained during the operation of the fan  2 . 
     Moreover, the airflow passage is enlarged to provide more space to let airflows pass through. A fan with a diameter of 40 mm, for example, may have a hub, normally with a diameter of 23 mm, to be reduced downward to 21 mm, without amending other components disposed within the fan  2 . Therefore, the airflow passage is able to be enlarged to increase the space for airflows to pass, enhancing heat dissipation efficiency. 
     Additionally, in order to have a better result for reducing noise, the ribs  27  between the fan frame and the base  21 , and the blades  42  are both designed to extend upwardly, restraining the pneumatic noise and upgrading the efficiency of the fan. Furthermore, the bottom peripheries of the blades  42  extend along an axial direction toward the air outlet of the fan and exceed a top periphery of the side wall  212  of the base, so that the size of the blades is increased, raising air volume produced. 
     Second Embodiment 
     The variation of the fan of the invention is not limited. Referring to  FIG. 3 , a schematic view of a fan according to a second embodiment of the present invention is shown. The stator of the fan  3  can be varied according to requirements. The structure of this embodiment is substantially the same as that of the previous embodiment. It differs in that the stator has a metal casing  31 , and a coil  32  is disposed between the metal casing  31  and the magnetic member  44  to achieve the same effect of the previous first embodiment. The coil  32  is fixed on a rack  33  so as to be disposed within the metal casing  31 . Besides, the bottom wall  211  does not have a protrusion, and a circuit board  25  without an opening is provided. The circuit board  25  is disposed in the first accommodating space  213  by being abutted with the at least one fastening structure. As a result, the center of the circuit board  25  does not require an additional opening, the area of the circuit board  25  can be fully utilized to assemble more components and heat dissipation efficiency of the circuit board  25  is raised. 
     As described, the fan of the present invention substantially lowers the rotating inertia, efficiently reduces noise, and widens the airflow path to enhance heat dissipation efficiency. The design can apply to variant fans, especially an axial fan, to elaborate its unique characteristics. 
     While the present invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the present invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.