Abstract:
A micro cooling fan includes a housing, a fan wheel, and a main circuit board. The main circuit board has a stator and a driving circuit. The stator is electrically connected to the driving circuit. The stator is disposed on a first inner surface, and the driving circuit is disposed on a first outer surface, so that the housing and the driving circuit of the micro fan motor form an integral structure. The first outer surface is opposite to the first inner surface, or the first outer surface is located on a side surface of the housing. Therefore, by disposing the driving circuit on the first outer surface, the wind resistance of the fan blades is reduced, and the air volume of the micro cooling fan is increased accordingly, so that the cooling effect of the micro cooling fan is improved.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 099117314 filed in Taiwan, R.O.C. on May 28, 2010, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a micro cooling fan, and more particularly to a micro cooling fan in which a driving circuit is disposed on an outer surface of a housing to achieve an integral structure of the housing and the driving circuit of a micro fan motor. 
     2. Related Art 
     In recent years, an electronic device is disposed with a variety of electronic elements, such as a central processing unit and a power supply. Since the electronic elements will generate a lot of heat when the electronic device is running, a cooling fan needs to be mounted to remove heat, so as to prevent the life of the electronic elements from being shortened due to an excessively high temperature of the electronic elements. 
     A direct current fan motor structure which is disclosed uses a control circuit device to control the electromagnetic effect of a stator device such that a rotor device is rotated by an electromagnetic repulsive force of the stator device. In the stator device, a hollow coil set is sleeved on a ring magnet of a magnetically conductive sleeve, and an upper silicon-steel sheet and a lower silicon-steel sheet of a silicon-steel sheet set are disposed on a top edge and a bottom edge of the magnetically conductive sleeve and the ring magnet respectively. The main characteristic lies in that a periphery of each silicon-steel sheet is provided with four symmetric protruding portions. Wherein, the four protruding portions of the upper silicon-steel sheet and the four protruding portions of the lower silicon-steel sheet are alternately arranged, and one side edge of each protruding portion is slightly larger than the other side edge, thereby forming an asymmetric design. Since the control circuit device is located below the stator and in an axial direction of the fan, poor heat dissipation is caused, resulting in that the life of electronic elements on the control circuit device is reduced. Moreover, since the area of the electronic elements disposed on the control circuit device is limited by a maximum outer diameter of the motor, it is difficult to arrange and dispose the electronic elements. 
     A cooling fan which is disclosed includes a frame and a fan wheel. The frame has an air-intake surface, an air-outlet surface, an inner annular wall, an axial air channel, and a bearing portion. The bearing portion is formed on at least a portion of a frame edge, and includes a first side wall, a second side wall, and a loading space. The first side wall is formed by at least a portion of the inner annular wall, and the second side wall is spaced apart from the first side wall. The loading space is formed between the first side wall and the second side wall, and is used to bear a driving circuit board. Since the driving circuit is placed in the loading space of the inner annular wall, the air volume of the cooling fan is increased, and the cooling problem of the driving circuit is solved. However, in the manufacturing process of the above cooling fan, the loading space needs to be disposed in the inner annular wall of the frame to place the driving circuit. The manufacturing process of the frame is complex, and a consideration has to be given to the cooling of the driving circuit. 
     In addition, when the cooling fan is used in an Internet terminal, the cooling fan needs to be miniaturized. However, in the miniaturization process of the cooling fan, a three-phase motor structure needs to be used so as to lower the power consumption of the cooling fan, and since the three-phase motor requires a larger disposition space than a single-phase motor, a problem regarding whether a micro cooling fan has an extra space for disposing the driving circuit is imposed. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is a micro cooling fan, in which a driving circuit and a housing of the micro cooling fan are integrated to form an integral structure, such that the wind resistance of the micro cooling fan is reduced, thereby improving the cooling effect of the micro cooling fan; no consideration needs to be given to the cooling of the driving circuit; and the problem that the micro cooling fan has no extra space for disposing the driving circuit is solved. 
     In an embodiment, the micro cooling fan comprises a housing, a fan wheel, and a main circuit board. The housing has an accommodation space, a first inner surface, and a first outer surface. The fan wheel has a plurality of fan blades and is disposed in the accommodation space. The main circuit board comprises a first circuit board and a second circuit board. A stator is disposed on the first circuit board, a driving circuit is disposed on the second circuit board, and the stator is electrically connected to the driving circuit. The first circuit board is disposed on the first inner surface, and the second circuit board is disposed on the first outer surface. 
     In another embodiment, the micro cooling fan comprises a housing and a main circuit board. The housing has an accommodation space, a first inner surface, and a gap. The gap is in communication with the accommodation space, and two opposite side edges of the gap have a groove respectively. The main circuit board comprises a first circuit board and a second circuit board. The first circuit board has a stator, the second circuit board has a driving circuit, and the stator is electrically connected to the driving circuit. The first circuit board is disposed on the first inner surface, and the second circuit board is embedded into the grooves and blocks the gap. 
     The micro cooling fan according to the above embodiments can be applied to an electronic device. The second circuit board on which the driving circuit is disposed may be directly disposed on the first outer surface of the housing, or be embedded into the housing and thus become a part of the housing. Owing to the above micro cooling fan, the driving circuit and the housing of the micro cooling fan are integrated to form an integral structure that makes no consideration of the cooling of the driving circuit, reduces the wind resistance of the micro cooling fan, and thereby improves the cooling effect of the micro cooling fan. In addition, the micro cooling fan solves the problem that no extra space can be provided for disposing the driving circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given herein below for illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1A  is a three-dimensional exploded view according to a first embodiment of the present invention; 
         FIG. 1B  is a three-dimensional assembled view according to the first embodiment of the present invention; 
         FIG. 2  is a schematic cross-sectional view along Line  2 - 2  in  FIG. 1B ; 
         FIG. 3  is a schematic view of a main circuit board according to the first embodiment of the present invention; 
         FIG. 4  is a three-dimensional exploded view according to a second embodiment of the present invention; 
         FIG. 5  is a schematic cross-sectional view according to a third embodiment of the present invention; 
         FIG. 6A  is a three-dimensional exploded view of an outer frame and a main circuit board according to a fourth embodiment of the present invention; 
         FIG. 6B  is a three-dimensional assembled view of the outer frame and the main circuit board according to the fourth embodiment of the present invention; 
         FIG. 7A  is a three-dimensional exploded view of an outer frame and a main circuit board according to a fifth embodiment of the present invention; and 
         FIG. 7B  is a three-dimensional assembled view of the outer frame and the main circuit board according to the fifth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1A  and  FIG. 1B  are respectively a three-dimensional exploded view and a three-dimensional assembled view according to a first embodiment of the present invention. Referring to  FIG. 1A  and  FIG. 1B , a micro cooling fan  100  comprises a housing  102 , a magnetic block  104 , a main circuit board  106 , a bearing  108 , and a fan wheel  110 . The housing  102  in this embodiment may be formed by two sub-housings, but is not limited thereto. As can be seen from the figures, the housing  102  is formed by an outer frame  112  and a top cover  114 . The housing  102  has an air-intake surface  116  and an air-outlet surface  118  opposite to each other, an air channel  120 , an accommodation space  122 , a bearing support  124 , a first inner surface  126 , and a first outer surface  128 . The air-intake surface  116  may be disposed on a surface of the top cover  114 , and the air-outlet surface  118  may be disposed on a surface of the outer frame  112 ; however, this embodiment is not intended to limit the present invention. For example, the air-intake surface  116  may be disposed on a surface of the outer frame  112 , and the air-outlet surface  118  may be disposed on a surface of the top cover  114 . 
       FIG. 2  is a schematic cross-sectional view along Line  2 - 2  in  FIG. 1B . Referring to  FIG. 2 , the air channel  120  is disposed between the air-intake surface  116  and the air-outlet surface  118 , and runs through the housing  102 . The micro cooling fan  100  achieves a cooling effect by guiding an air flow to flow through the air channel  120  (that is, in a direction pointed by arrows in  FIG. 2 ). The accommodation space  122  is used to place the magnetic block  104 , the main circuit board  106 , and the fan wheel  110 . The fan wheel  110  is pivoted to the bearing support  124  by the bearing  108 , and can rotate relative to the air-outlet surface  118 . The fan wheel has five fan blades  1101 , but the number of the fan blades  1101  is not limited thereto. The bearing support  124  and the magnetic block  104  are disposed on the first inner surface  126 . The magnetic block  104  is used to increase the magnetic flux density in the air gap. 
     The first inner surface  126  may be a surface surrounding the accommodation space  122 , such as an inner bottom surface  126   a  and an inner annular wall  126   b . The first outer surface  128  may be a surface of the housing  102  in contact with an external environment, such as four outer side surfaces  128   a ,  128   b ,  128   c , and  128   d , and an outer bottom surface  128   e  (see  FIG. 1A  and  FIG. 2 ). In this embodiment, the first inner surface  126  is a surface surrounding the accommodation space  122  and opposite to the air-outlet surface  118  in the outer frame  122  (that is, the inner bottom surface  126   a ), the first outer surface  128  is an outer side surface in the housing  102  (that is, the outer side surface  128   a ), and the first outer surface  128  is perpendicular to the air-outlet surface  118  and the air-intake surface  116 ; however, this embodiment is not intended to limit the present invention. 
       FIG. 3  is a schematic view of a main circuit board according to the first embodiment of the present invention. Referring to  FIG. 3 , the main circuit board  106  comprises a first circuit board  1061  and a second circuit board  1062 . The main circuit board  106  may be an integral circuit board (that is, the first circuit board  1061  and the second circuit board  1062  are the same circuit board), or a combined circuit board (that is, the first circuit board  1061  and the second circuit board  1062  are combined into the main circuit board  106 ). In this embodiment, the first circuit board  1061  and the second circuit board  1062  are the same circuit board, and an embodiment in which the first circuit board  1061  and the second circuit board  1062  are combined into the main circuit board  106  will be described in detail later. 
     The design of the first circuit board  1061  and the second circuit board  1062  are integrated, i.e. during the layout and production process, the first circuit board  1061  is connected to the second circuit board  1062 . The first circuit board  1061  may use a flexible circuit board to be electrically connected to the second circuit board  1062 . Therefore, during assembling process, it is easy to dispose the first circuit board  1061  in the accommodation space  122 , and dispose the second circuit board  1062  on the first outer surface  128  of the housing  102 . 
     Referring to  FIG. 2 , a stator  130  is disposed on the first circuit board  1061 , and a driving circuit  132  is disposed on the second circuit board  1062 . The stator  130  may be, but is not limited to, a set of stator coils. The driving circuit  132  comprises a connecting terminal  134  and a driving element  136 . The stator  130  is electrically connected to the driving circuit  132 , and the driving circuit  132  is connected to an external power by the connecting terminal  134 , such that the driving element  136  generates a driving current to drive the stator  130  (that is, a set of stator coils). The driven stator  130  generates a magnetic field to drive the fan wheel  110  to rotate. 
     Furthermore, the second circuit board  132  comprises a first plate portion  151  and a second plate portion  152  perpendicular to the first plate portion, and the first plate portion  151  of the second circuit board  132  covers one side of the first outer surface  128 . 
     In this embodiment, since the stator  130  and the fan wheel  110  are disposed on the first inner surface  126 , the area of the stator  130  and the fan wheel  110  is smaller than or equal to the area of the first inner surface  126 , so as to reduce the wind resistance when air flows into or out of the air channel  120 . By disposing the driving circuit  132  on the first outer surface  128 , the problem that the micro cooling fan has no extra space for disposing the driving circuit is solved, and the cooling effect can be achieved by thermal convection between the driving circuit  132  and the external environment. 
     Referring to  FIG. 1A  and  FIG. 3 , in this embodiment, the outer frame  112  further has an opening  138  and a rib  140 , and the first circuit board  1061  has a connecting board  142 . The opening  138  is a position for placing the connecting board  142  such that the connecting board  142  connects the first circuit board  1061  and the second circuit board  1062 . The connecting board  142  is disposed on the rib  140 , and the width of the connecting board  142  is smaller than or equal to the width of the rib  140 , so as to reduce the wind resistance when air flows into or out of the air channel  120 . The micro cooling fan  100  refers to a micro cooling fan having a length less than twenty centimeters, a width less than twenty centimeters, and a height less than ten centimeters. 
       FIG. 4  is a three-dimensional exploded view according to a second embodiment of the present invention. Referring to  FIG. 4 , a micro cooling fan  200  comprises a housing  202 , a magnetic block  204 , a first circuit board  206 , a second circuit board  208 , a bearing  210 , and a fan wheel  212 . The housing  202  is formed by two sub-housings. In other words, the housing  202  is formed by an outer frame  214  and a top cover  216 . The first circuit board  206  and the second circuit board  208  are combined into a main circuit board  218 . A stator  220  is disposed on the first circuit board  206 , a driving circuit  222  is disposed on the second circuit board  208 , and the stator  220  is electrically connected to the driving circuit  222 . The stator  220  may be, but is not limited to, three sets of stator coils. The driving circuit  222  comprises a connecting terminal  224  and a driving element  226 . Both the first circuit board  206  and the second circuit board  208  may be flexible substrates, or the first circuit board  206  is a flexible substrate while the second circuit board  208  is a rigid substrate, which can be selected according to practical requirements. 
       FIG. 5  is a schematic cross-sectional view according to a third embodiment of the present invention. Referring to  FIG. 5 , a micro cooling fan  300  comprises a housing  302 , a magnetic block  304 , a first circuit board  306 , a second circuit board  308 , a bearing  310 , and a fan wheel  312 . The housing  302  has an air-intake surface  316  and an air-outlet surface  318  opposite to each other, an air channel  320 , a bearing support  324 , a first inner surface  326 , and a first outer surface  328 . The housing  302  is formed by an outer frame  3021  and a top cover  3022 . The air-intake surface  316  may be disposed on a surface of the top cover  3022 , and the air-outlet surface  318  may be disposed on a surface of the outer frame  3021 ; however, this embodiment is not intended to limit the present invention. 
     A main circuit board  330  comprises a first circuit board  306  and a second circuit board  308 , and the first circuit board  306  and the second circuit board  308  are the same circuit board. A stator  332  is disposed on the first circuit board  306 , a driving circuit  334  is disposed on the second circuit board  308 , and the stator  332  is electrically connected to the driving circuit  334 . The driving circuit  334  comprises a connecting terminal  336  and a driving element  338 . The first circuit board  306  is disposed on the first inner surface  326 , and the second circuit board  308  is disposed on the first outer surface  328 . In this embodiment, the first inner surface  326  and the first outer surface  328  may be two opposite side surfaces of the air-outlet surface  318 , and the first inner surface  326  is a surface surrounding the air channel  320 . 
       FIG. 6A  and  FIG. 6B  are respectively a three-dimensional exploded view and a three-dimensional assembled view of an outer frame and a main circuit board according to a fourth embodiment of the present invention. Referring to  FIG. 6A  and  FIG. 6B , a micro cooling fan  400  comprises a housing and a main circuit board  401 , and the housing is an outer frame  402 . The outer frame  402  has an accommodation space  404 , a first inner surface  406 , an air-outlet surface  407 , and a gap  408 . The gap  408  is in communication with the accommodation space  404 , and two opposite side edges of the gap  408  have grooves  410  and  412  respectively. In this embodiment, the first inner surface  406  is a surface surrounding the accommodation space  404  in the outer frame  402  and opposite to the air-outlet surface  407 . 
     A main circuit board  401  comprises a first circuit board  416  and a second circuit board  418 . The first circuit board  416  has a stator  420 , and the second circuit board  418  has a driving circuit  422 , and the stator  420  is electrically connected to the driving circuit  422 . The first circuit board  416  is disposed on the first inner surface  406 , and the second circuit board  418  is embedded into the grooves  410  and  412  and blocks the gap  408 . In other words, the second circuit board  418  becomes a part of the outer frame  402 . The stator  420  may be, but is not limited to, three sets of stator coils. The driving circuit  422  comprises a connecting terminal  424  and a driving element  426 . 
       FIG. 7A  and  FIG. 7B  are respectively a three-dimensional exploded view and a three-dimensional assembled view of an outer frame and a main circuit board according to a fifth embodiment of the present invention. Referring to  FIG. 7A  and  FIG. 7B , a micro cooling fan  500  comprises a housing and a main circuit board  501 , and the housing is an outer frame  502 . The outer frame  502  has an accommodation space  504 , a first inner surface  506 , an air-outlet surface  507 , and a gap  508 . The gap  508  is in communication with the accommodation space  504 , and two opposite side edges of the gap  508  have grooves  510  and  512  respectively. 
     A main circuit board  501  comprises a first circuit board  516  and a second circuit board  518 . The first circuit board  516  has a stator  520 , the second circuit board  518  has a driving circuit  522 , and the stator  520  is electrically connected to the driving circuit  522 . The first circuit board  516  is disposed on the first inner surface  506 , and the second circuit board  518  is embedded into the grooves  510  and  512  and blocks the gap  508 . The stator  520  may be, but is not limited to, three sets of stator coils. The driving circuit  522  comprises a connecting terminal  524  and a driving element  526 . 
     In this embodiment, the outer frame  502  has an inner annular wall  528  and a bearing support  530 , and the inner annular wall  528  is in a form of an arc-shaped surface. The arc-shaped surface has an arc angle of 270 degrees to 330 degrees, and an axle center of the arc is parallel to the bearing support  530  of the micro cooling fan  500 . The arc angle of the arc-shaped surface affects the wind resistance when air flows into or out of the outer frame  502 , and the larger the arc angle of the arc-shaped surface is, the smaller the wind resistance will be. The second circuit board  518  that is embedded into the grooves  510  and  512  and blocks the gap  508  may be, but is not limited to, a rigid circuit board. 
     Based on the above, the micro cooling fan according to the above embodiments can be applied to an electronic device. The second circuit board on which the driving circuit is disposed may be directly disposed on the first outer surface of the housing, or be embedded into the housing and thus become a part of the housing. Owing to the above micro cooling fan, the driving circuit and the housing of the micro cooling fan are integrated to form an integral structure that makes no consideration for the cooling of the driving circuit, reduces the wind resistance of the micro cooling fan, thereby improves the cooling effect of the micro cooling fan, and solves the problem that the next-generation micro cooling fan has no extra space for disposing the driving circuit.