Patent Publication Number: US-9429168-B2

Title: Fan and frame thereof

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 096118685, filed in Taiwan, Republic of China on May 25, 2007, 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 fan and a frame thereof, and more particularly to a fan and a frame thereof for guiding airflow away from the fan and reducing vortex. 
     2. Description of the Related Art 
     As the performance of electronic devices continue to enhance, heat dissipating devices and heat dissipating systems are playing more critical roles within the electronic devices. Poor heat dissipation can lead to damage or failure to the electronic devices. 
     Heat dissipating devices play an even more important role for microelectronic elements and devices, (e.g. integrated circuit, IC). Due to the increase of integration and advancement of packaging technology, integrated circuit area keeps being reduced and heat per unit area thus keeps being increased. Thus, high efficient heat dissipating devices have been under active development by those in the field. 
     Referring to  FIG. 1A , a cross section view of a conventional axial fan and  FIG. 1B , a schematic illustration of a direction of airflow of  FIG. 1A  are shown. Generally, an axial fan  1  has a frame  11  and a motor base  14  which are connected to each other by several ribs  13 . When an airflow f enters an airflow inlet  16  of an axial fan  1  in a vertical direction (as shown in  FIG. 1B , arrow X 1 ), an impeller  12  of the axial fan  1  rotates to change the original direction of the airflow f (as shown in  FIG. 1B , arrow X 2 ). Then the airflow f passes through the ribs  13  (as shown in  FIG. 1B , arrow X 3 ). However, the ribs  13  can not completely guide the airflow back to the vertical direction. Thus, the airflow f of the axial fan  1  exiting from the airflow outlet  17  is not in the vertical direction, as indicated by arrow X 4  in  FIG. 1B . The airflow f has a tangent component which causes vortex v. Therefore, loss of kinetic energy of the axial fan  1  is raised, and efficiency of heat dissipation is reduced. If more axial fans  1  are provided to achieve adequate heat dissipation effect, then costs and noise will be increased. In addition, axial fans  1  are heat sources. It requires additional energy to dissipate heat generated from the axial fans. 
     BRIEF SUMMARY OF THE INVENTION 
     To solve the problems of the conventional axial fan, the present invention provides a fan and a frame thereof, wherein airflow can be guided vertically to the airflow outlet and away from the fan. Therefore, vortex is reduced, resulting in higher heat dissipating efficiency and lower noise. 
     To achieve the above, the present invention discloses a frame. The frame includes a main body and a plurality of guiding elements. The main body has an airflow inlet and an airflow outlet. The guiding elements are disposed in the main body and located at the airflow outlet. Each of the guiding elements includes an inclined part and an axial extended part, and the inclined part meets the axial extended part at an angle. The guiding elements guide an airflow away from the frame by passing through the inclined part and the axial extended part in turn. 
     To achieve the above, the present invention discloses a fan. The fan includes a frame, and an impeller. The frame includes a main body, a plurality of guiding elements and a motor base. The main body has an airflow inlet and an airflow outlet. The guiding elements are disposed in the main body and located at the airflow outlet. Each of the guiding elements includes an inclined part and an axial extended part, and the inclined part meets the axial extended part at an angle. The impeller is disposed on the motor base for providing an airflow, and then the guiding elements guide the airflow away from the fan by passing through the inclined part and the axial extended part in turn. 
     For the above descriptions of the fan and the frame thereof, the angle is between 20 degrees and 50 degrees. The inclined part has a first height, the axial extended part has a second height, and a ratio of the first height and the second height is between 0.2 and 5. The sum of the first height and the second height exceeds 15 millimeters. The axial extended part parallels an axis of the frame or inclines to the axis of the frame by a clipping angle which is smaller than or equal to 20 degrees. A cross-section of the inclined part is wing shaped, arc-shaped or streamline-shaped. The inclined part and the axial extended part are integrally formed as a single piece or different components and combined to form the guiding element. The frame further includes a motor base connected to the main body via the guiding elements. The motor base has at least one protruding rib inside the motor base. The main body is substantially rectangular, rounded, elliptic, polygonal or cone-shaped. 
     For the above descriptions, the fan further includes a driving element installed on the motor base. The driving element rotates the impeller to form the airflow. The driving element can be a motor, and the impeller has a hub and a plurality of blades. 
    
    
     
       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. 1A  is a cross section view of a conventional axial fan. 
         FIG. 1B  is a schematic illustration showing the direction of airflow of the conventional axial fan in  FIG. 1A . 
         FIG. 2A  is a schematic illustration of a fan in accordance with an embodiment of the present invention. 
         FIG. 2B  is a schematic illustration of the frame of  FIG. 2A . 
         FIG. 2C  is a cross section view of the fan of  FIG. 2A . 
         FIG. 3A  is a vertical cross section view of the guiding element of  FIG. 2B . 
         FIG. 3B  is a schematic illustration showing the direction of airflow of  FIG. 2A   
         FIG. 4  is a schematic diagram showing efficiency curves of a conventional axial fan and an axial fan according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 2A , a schematic illustration of a fan in accordance with an embodiment of the present invention,  FIG. 2B , a schematic illustration of the frame of  FIG. 2A , and  FIG. 2C , a cross section view of the fan of  FIG. 2A  are shown. The fan  2  includes a frame  21  and an impeller  22 . The frame  21  includes a main body  25 , a plurality of guiding elements  23  and a motor base  24 . The main body  25  has an airflow inlet  26  and an airflow outlet  27 . The shape of the main body  25  can be different types depending on practical requirements. For example, the main body  25  may be substantially rectangular, rounded, elliptic, polygonal, cone-shaped or other shapes. The impeller  22  has a hub  221  and a plurality of blades  222 . The motor base  24  has at least one protruding rib  28  inside the motor base  24  for increasing the structural strength of the motor base  24 . The impeller  22  is disposed on the motor base  24 . A driving element (e.g. motor, not shown) is also installed on the motor base  24 . The driving element rotates the impeller  22  to form an airflow. Then, the guiding elements  23  guide the airflow away from the airflow outlet  27  of the fan  2 . 
       FIG. 3A  is a vertical cross section view of the guiding element of  FIG. 2B . Referring to  FIG. 2C  and  FIG. 3A , the guiding elements  23  are disposed in the main body  25  and located at the airflow outlet  27 . Each of the guiding element  23  includes an inclined part  231  and an axial extended part  232 , and the inclined par  231  meets the axial extended part  232  at an angle “a”, which is between 20 degrees and 50 degrees. The angle “a” may be changed in accordance with the characteristic of the fan  2 . The axial extended part  232  can be parallel to a vertical direction “X” of the frame or incline to the axis of the frame  21  by a clipping angle which is smaller than or equal to 20 degrees. In order to allow airflow smoothly through the fan, a cross-section of the inclined part  231  is designed as wing shaped, arc-shaped or streamline-shaped. Therefore, the airflow passes through the inclined part  231 , which is streamline-shaped, will reduce friction produced by airflow and decrease kinetic energy loss. Then, the airflow leaves the fan  2  after passing through the axial extended part  232 . As shown in  FIG. 3A , the inclined part  231  has a first height H 1 , the axial extended part  232  has a second height H 2 . If a ratio of the first height H 1  to the second height H 2  is between 0.2 and 5, then the guiding elements  23  can function well. Furthermore, the first height H 1  of the inclined part  231  and the second height H 2  of the axial extended part  232  are determined by the size of the fan  2 . For example, the efficiency for a fan sized as 38*38 millimeters is optimized if the sum of the first height H 1  of the inclined part  231  and the second height H 2  of the axial extended part  232  exceeds 15 millimeters. 
     Referring to  FIG. 3B , a schematic illustration showing of the direction of airflow of  FIG. 2A  is shown. When the fan  2  operates, the airflow f′ outside the fan  2  enters the airflow inlet  26  in a vertical direction (as shown in  FIG. 3B , arrow X 1 ′). Then, the airflow f′ is guided by the blades  222  on the circumference of the hub  221  to increase its pressure and velocity. Thus, the direction of the airflow is changed (as shown in  FIG. 3B , arrow X 2 ′). The velocity of the airflow f′ includes a tangent velocity component and a vertical velocity component, and the tangent velocity component and the vertical velocity component interfere with each other to form a vortex. To avoid a vortex, therefore, the position of the guiding elements  23  is arranged to comply with the direction of the airflow f′, wherein the inclined angle of the inclined parts  231  is approximately equal to that of the airflow f′. Furthermore, the inclined parts  231  and the axial extended parts  232  constitute a streamlined wing structure. Thus, after passing through the inclined parts  231  of the guiding elements  23 , the airflow f′ can be smoothly guided to the location where the inclined part  231  and the axial extended part  232  meet. Meanwhile, the tangent velocity component of the airflow f′ is partially converted into the vertical velocity component as indicated by arrow X 3 ′ in  FIG. 3B . Then, the airflow f is guided by the axial extended parts  232  to completely convert the tangent velocity component into the vertical velocity component as indicated by arrow X 4 ′ in  FIG. 3B . Finally, the airflow f′ exits from the airflow outlet  27  of the fan  2 . Thus, the vortex phenomenon of the airflow outlet  27  of the fan  2  can be completely controlled. Therefore, the pressure and velocity of the fan  2  can be increased. 
     The guiding elements  23  of the present invention can be implemented in various ways. For example, the guiding elements  23  are integrally formed with the frame  21  as a single piece. For another example, the guiding elements  23  are formed by combining the inclined parts  231  and the axial extended parts  232  which are two separate components before combining. Or, the axial extended parts  232  are integrally formed with the frame  21  as a single piece and then are combined to the inclined part  231  of other component. The guiding elements  23  formed by combining the inclined parts  231  of one component and the axial extended parts  232  of other component facilitate a replacement of the damaged part therefrom, and allow the manufacturers to select different inclined parts  231  and axial extended parts  232  in accordance with different shapes of impellers  22  so as to increase the heat dissipating efficiency of the fan  2 . For the above design, the axial extended part  232  and the inclined part  231  can be separate components and then be assembled. It is convenient that the design not only allows the fan  2  to replace a damaging part easily but also increases flexibility of choosing of the appropriate inclined part  231  and the axial extended part  232  according to the shape of the impeller  22 . 
       FIG. 4  is a schematic diagram showing efficiency curves of a conventional axial fan and an axial fan according to the embodiment of the present invention. In the embodiment of the present invention, the guiding elements  23  are provided to solve the problem of the flow field arising from the vortex produced at the airflow outlet  27  of the fan  2 . Thus, pressure and velocity of the airflow is raised to enhance the overall performance of the fan  2  (as marked in  FIG. 4 ). Moreover, the guiding elements  23  can be assembled by various designs to expand the applicable scope of the fan  2 . 
     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 to the disclosed embodiments. 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.