Patent Publication Number: US-2007116573-A1

Title: Fan and impeller thereof

Description:
BACKGROUND OF THE INVENTION  
      1. Field of Invention  
      The invention relates to a fan and an impeller thereof and, in particular, to a fan and an impeller thereof having downward-shifted blades.  
      2. Related Art  
      With the high development of technologies, the requirements for the functions of the electronic products become more critical and complex. Accordingly, the number of electronic elements in the electronic product and the integration of the electronic elements are increased, which results in the growing demands for heat dissipation. In other words, the heat dissipation capability directly affects the reliability and lifetime of the electronic product.  
      Fan is commonly used as a heat dissipating device. In practice, the working area of the fan, which is the area that can provide proper airflow pressure and airflow quantity of the fan, is used to remove heat rather than the maximum airflow quantity or the maximum airflow pressure. If a user wants to enhance the performance of the fan in the working area, he or she must increase the rotation speed of the fan. However, this may cause louder noise and need increased power consumption.  
      With reference to  FIG. 1 , a conventional fan  1  includes a fan frame  11 , an impeller  12  and a motor  13 . The impeller  12  includes a hub  121  and a plurality of blades  122  disposed around the hub  121 . The motor  13  is used to drive the impeller  12  to rotate. As shown in  FIG. 1 , the top edge of the impeller  12  and the top boundary of the fan frame  11  are almost at the same plane. When the fan  1  starts to rotate, the impeller  12  may move upwardly or have displacement due to the accompanying axial and centrifugal force. Thus, the blades  122  of the impeller  12  easily contact the case of the electronic product or other elements. In such a case, the fan  1  may be damaged, and the heat dissipating effect of the electronic product may be decreased.  
      Therefore, it is an important subject of the invention to provide a fan and an impeller thereof that can enhance the performance of the working area without increasing the rotation speed of the fan and can prevent the blades from contacting the electronic product or other elements.  
     SUMMARY OF THE INVENTION  
      In view of the foregoing, the invention is to provide a fan and an impeller thereof that can enhance the performance of the working area without increasing the rotation speed of the fan and can prevent the blades from contacting the electronic product or other elements in an electronic system.  
      To achieve the above, an impeller of the invention includes a hub and a plurality of blades. The blades are disposed around the hub. Each blade has a leading edge with a predetermined distance below the top of the hub and a trailing edge protruding from the bottom of the hub.  
      To achieve the above, the invention also discloses a fan, which includes a fan frame, an impeller and a motor. In the invention, the fan frame includes a housing, a base and at least one supporting element. The base is connected to the housing by the supporting element. The impeller, which is disposed in the housing, includes a hub and a plurality of blades disposed around the hub. Each blade has a leading edge with a predetermined distance below the top of the hub and a trailing edge protruding from the bottom of the hub. The motor is disposed on the base and coupled to the impeller for driving it.  
      As mentioned above, each blade of the impeller has a leading edge with a predetermined distance below the top of the hub, so that when the fan is operated, a space formed among the housing, the blades and the hub can make airflow steadier to be expelled out of the blades. In this case, the airflow pressure and the airflow quantity in the working area are larger than those of the conventional fan. That is, the performance of the working area of the fan can be enhanced without increasing the rotation speed of the fan. Accordingly, the louder noise and the increased power consumption can be avoided, and the better heat dissipating effect can be achieved. Besides, since displaced downwardly, the blades of the impeller, which is raised due to the axial and centrifugal force, may not contact the electronic product or other elements, so as to prevent the malfunctions of the fan, such as being stuck. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will become more fully understood from the detailed description given herein below illustration only, and thus is not limitative of the present invention, and wherein:  
       FIG. 1  is a schematic illustration showing a conventional fan;  
       FIG. 2  is a schematic illustration showing an impeller according to a preferred embodiment of the invention;  
       FIG. 3  is a schematic illustration showing a fan according to the embodiment of the invention;  
       FIG. 4  is a schematic illustration showing another fan according to the embodiment of the invention;  
       FIG. 5  is a coordinate diagram showing the performances of the conventional fan and the fan of the present invention; and  
       FIG. 6  is a schematic illustration showing an impeller according to another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.  
      With reference to  FIG. 2 , an impeller  2  according to a preferred embodiment of the invention includes a hub  21  and a plurality of blades  22  disposed around the hub  21 . The hub  21  and the blades  22  are integrally formed.  
      Each of the blades  22  has a leading edge  221  and a trailing edge  222 . In this embodiment, the leading edge  221  and the trailing edge  222  are in parallel. The leading edge  221  has a predetermined distance h below the top  211  of the hub  21 , and the trailing edge  222  protrudes from the bottom  212  of the hub  21 . Accordingly, all of the blades  22  are moved downwardly. In the embodiment, the hub  21  and the blades  22  may be made of a plastic material, an acrylic material, a metal, or an alloy.  
      With reference to  FIG. 3 , a fan  3  according to the embodiment of the invention includes a fan frame  31 , an impeller  32 , and a motor  33 . According to the concept of the invention, the type of the fan  3  is not limited, and it is an axial-flow fan in this embodiment.  
      The fan frame  31  has a housing  311 , a base  312  and at least one supporting element  313 . The supporting element  313  is, for example, a rib or a stationary blade, and the base  312  is connected to the housing  311  by the supporting element  313 . In this case, the housing  311 , base  312  and supporting element  313  are integrally formed, and the bottom  3131  of the supporting element  313  and the bottom  3111  of the housing  311  are placed at the same plane. Of course, the bottom  3131  of the supporting element  313  and the bottom  3111  of the housing  311  may be placed at different planes. For instance, the bottom  3131  of the supporting element  313  may be shifted toward the interior of the housing  311  as shown in  FIG. 4 . To be noted, the position of the supporting element  313  has to be limited to such that it cannot interrupt or affect the rotation of the impeller  32 . The housing  311 , base  312  and supporting element  313  are made of, for example and not limited to, a plastic material, an acrylic material, a metal, or an alloy.  
      The impeller  32  is disposed in the housing  311  and supported by the base  312 . In addition, the impeller  32  includes a hub  321  and a plurality of blades  322  disposed around the hub  321 . The hub  321  and the blades  322  are integrally formed. Herein, the materials of the hub  321  and the blades  322  are not limited, and they may be made of a plastic material, an acrylic material, a metal, or an alloy. The motor  33  is disposed on the base  312  and coupled to the impeller  32  for driving it to rotate.  
      Each of the blades  322  has a leading edge  3221  and a trailing edge  3222 . In this embodiment, the leading edge  3221  and the trailing edge  3222  are in parallel. The leading edge  3221  has a predetermined distance h below the top  3211  of the hub  321 . In the embodiment, the predetermined distance h is preferably between 15% and 22.5% of the height H of the hub  321 . In addition, the predetermined distance h is also preferably between approximately 8% and 12% of the height H′ of the housing  311 . The trailing edge  3222  protrudes from the bottom  3212  of the hub  321 . The protruding height of the trailing edge  3222  is approximately equal to the predetermined distance h, so that the blades  322  are substantially moved downwardly. Due to the provided distance h, the housing  311 , the blades  322  and the hub  321  can define a space. When the fan  3  is operated, the flowing air becomes a steady airflow in this space. Accordingly, the performance of the working area of the fan  3  can be enhanced; that is, the airflow pressure and the airflow quantity in the working area become larger than those of the conventional fan.  
       FIG. 5  is a coordinate diagram showing the performances of the conventional fan and the fan of the invention. As shown in  FIG. 5 , the X axis represents the airflow quantity, and the Y axis represents the airflow pressure. The triangular area represents the working area of the fans. Under the rotation speed of 4500 RPM, the experimental data of the  FIG. 5  show that the fan of the invention can efficiently increase the airflow pressure. As a result, the performance of the fan of the invention is better than that of the conventional fan.  
      To be noted, the blades of the impeller are unnecessary to have the leading edge  221  and the trailing edge  222  in parallel (as shown in  FIG. 2 ). The blades  22  may have the trailing edge  222  with a gradually raising slope from the inner edge to the outer edge thereof (as shown in  FIG. 6 ). Of course, the blades  22  may have the trailing edge  222  with a gradually descending slope from the inner edge to the outer edge thereof (not shown).  
      In summary, each blade of the impeller has a leading edge with a predetermined distance below the top of the hub, so that a space can be formed among the housing, the blades and the hub. When the fan is operated, the flowing air becomes a steady airflow in this space and is then blown out of the blades. In this case, the airflow pressure and the airflow quantity in the operating area are larger. That is, the performance of the working area of the fan can be enhanced without increasing the rotation speed of the fan. Accordingly, the louder noise and the increased power consumption can be avoided, and the better heat dissipating effect can be achieved Besides, since displaced downwardly, the blades of the impeller, which is raised due to the axial and centrifugal force, may not contact electronic product or other elements to avoid the malfunctions of the fan, such as being stuck.  
      Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.