Abstract:
A flow-guiding device, connected between two fans disposed in series and rotating in the same rotation direction, includes a main frame and a plurality of flow-guiding pieces. The flow-guiding pieces are connected with the main frame. Each of the flow-guiding pieces is disposed corresponding to the stationary flow guiding device of the above fan so as to form a completed flow guiding device. A fan assembly including the flow-guiding device is also disclosed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 095145987 filed in Taiwan, Republic of China on Dec. 8, 2006, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The invention relates to a flow-guiding device and a fan assembly. In particular, the invention relates to a flow-guiding device and a fan assembly with better efficiency. 
         [0004]    2. Related Art 
         [0005]    As electronic devices have better performance, operate at higher frequencies and speeds, and become more compact, they generally generate more heat. They are therefore likely to be unstable, lowering the reliability thereof. Therefore, heat dissipation is an important issue of the field. Using the fan as a heat dissipating device is a common solution. To enhance heat dissipation, several fans are often connected in series. 
         [0006]    As shown in  FIG. 1 , a conventional fan assembly  1  consists of an above fan  11  and a below fan  12  connected in series. The above fan  11  has a fan frame  111  and an impeller  112  disposed inside the fan frame  111 . It also has several blades  1121  and a hub  1122  connected with each other. The above fan  11  further has several static blades  113  connected with the fan frame  111 . The below fan  12  also has a fan frame  121 , an impeller  122 , and several static blades  123 . The impeller  122  also has several blades  1221  and a hub  1222 . The structure of the below fan  12  is the same as the above fan  11 . They rotate in the same direction (as indicated by the arrow in  FIG. 1 ). The fan assembly  1  is shown in  FIG. 2 . 
         [0007]    The airflow in the fan assembly  1  is illustrated in  FIG. 3 , where the rotation direction R of the blades is also indicated. When the above fan  11  rotates, airflow goes from the blades  1121  to the static blades  113 . Once the airflow is guided by the static blades  113  to the below fan  12 , it goes to the low pressure area L of the blades  1221 . This reduces the pressure difference between the high pressure area H and the low pressure area L of the blades  1221 . Moreover, the airflow guided by the static blades is almost perpendicular to the blades  1221 . These factors greatly reduce the efficiency of the below fan  12 . Therefore, the air pressure and quantity output by the fan assembly are reduced. 
       SUMMARY OF THE INVENTION 
       [0008]    In view of the foregoing, the invention is to provide a flow-guiding device and a fan assembly that can increase the output air pressure and quantity and thus the entire performance. 
         [0009]    To achieve the above, the invention discloses a flow-guiding device connected between two series fans rotating in the same direction. The flow-guiding device includes a frame and a plurality of flow-guiding pieces connected with the frame. Each of the flow-guiding pieces and a corresponding static blade of the above fan form a flow-guiding element. 
         [0010]    To achieve the above, the invention also discloses a fan assembly including two fans and a flow-guiding device. The fans rotate in the same direction and are connected in series. The flow-guiding device is connected between the two fans and has a frame and several flow-guiding pieces connected to the frame. Each of the flow-guiding pieces and a corresponding static blade of the above fan form a flow-guiding element. 
         [0011]    As mentioned above, in the flow-guiding device and fan assembly of the invention, the flow-guiding elements are formed by several flow-guiding pieces and the static blades of the above fan. This does not only enhance the flow-guiding effect of the static blades, but also greatly increase the efficiency of the below fan. The output air pressure and quantity and thus the overall performance of the fan assembly become much better than the prior art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    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: 
           [0013]      FIG. 1  is an exploded view of the conventional fan assembly; 
           [0014]      FIG. 2  shows the fan assembly of  FIG. 1 ; 
           [0015]      FIG. 3  shows the airflow in the fan assembly of  FIG. 2 ; 
           [0016]      FIG. 4  is an exploded view of the fan assembly according to an embodiment of the invention; 
           [0017]      FIG. 5  shows the fan assembly in series of  FIG. 4 ; 
           [0018]      FIG. 6  shows the airflow in the fan assembly of  FIG. 5 ; and 
           [0019]      FIG. 7  shows the fan performance curve comparing the conventional fan assembly with the fan assembly of the embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    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. 
         [0021]    As shown in  FIG. 4 , the fan assembly  2  according to an embodiment of the invention includes two fans  21 ,  22  and a flow-guiding device  23 . The fans  21 ,  22  are connected in series and rotate in the same direction (as indicated by the arrow). The flow-guiding device  23  is connected between the fans  21 ,  22  and has a frame  231  and several flow-guiding pieces  232 . One end of each flow-guiding piece  232  is connected with the frame  231 . Moreover, the flow-guiding device  23  further includes a connecting part  233 . The other end of the flow-guiding piece  232  is connected with the connecting part  233 . The flow-guiding pieces  232  in this embodiment can be disposed in a symmetric or asymmetric way. 
         [0022]    In this embodiment, the fan  21  is the above fan and the fan  22  is the below fan. The fan  21  has a fan frame  211 , an impeller  212  disposed inside the fan frame  211 , several blades  2121 , and a hub  2122 . The blades  2121  are connected to the hub  2122 . Besides, the fan  21  further has several static blades  213  connected with the fan frame  211 . The fan  22  also has a fan frame  221 , an impeller  222  disposed inside the fan frame  221 , several blades  2221 , and a hub  2222 . The blades  2221  are connected to the hub  2222 . The fan  22  further has several static blades  223  connected with the fan frame  221 . In this embodiment, the fans  21 ,  22  can be axial-flow fans. They may have same or different structures. However, the rotation directions have to be the same. 
         [0023]    The frame  231  of the flow-guiding device  23  is connected to the fan frames  211 ,  221  of the fans  21 ,  22 . The connection method can be fastening, locking, embedding, or gluing. The fan assembly  2  connected in series is shown in  FIG. 5 . 
         [0024]    The airflow of the fan assembly  2  is illustrated in  FIG. 6 , where the rotation direction R of the blades is also indicated. Once the fan assembly  2  is assembled, each flow-guiding piece  232  and a corresponding static blade  213  of the fan  21  form a flow-guiding element. Here the number of the flow-guiding pieces  232  and the number of the static blades  213  are the same. In this embodiment, the flow-guiding piece  232  and the static blades  213  of the fan  21  have a half crescent cross-section. The combination of the static blades  213  and the flow-guiding pieces  232  forms crescent air-guiding elements. It should be noted that the crescent-guiding element mentioned above is only one example of the invention. The numbers and shapes of the flow-guiding pieces  232  and the static blades  213  do not need to be same. The shape of the flow-guiding pieces  232  can be different from that of the static blades  213 . Besides, the flow-guiding piece  232  has shrinking, expanding or constant thickness. 
         [0025]    When the fan  21  rotates, airflow is induced to flow from the blades  2121  to the static blades  213  and the flow-guiding pieces  232 . The flow-guiding elements formed by the static blades  213  and the flow-guiding pieces  232  not only guide the airflow to enhance the fan efficiency, but also connect the high pressure areas H of the outlet of the above fan and inlet of the below fan. The performance of the invention is much better than that of the fan assembly with only static blades  213 . 
         [0026]    Please refer to  FIG. 7 . It shows the experimental comparison between the conventional fan assembly  1  and the disclosed fan assembly  2  with the flow-guiding device  23 . The horizontal axis represents the air quantity, and the vertical axis represents the air pressure. The fan performance curve shows that the invention outputs larger air pressure and quantity at the same rotation speed. 
         [0027]    In summary, in the flow-guiding device and fan assembly of the invention, the flow-guiding elements are formed by several flow-guiding pieces and the static blades of the above fan. This does not only enhance the flow-guiding effect of the static blades, but also greatly increase the efficiency of the below fan. The output air pressure and quantity and thus the overall performance of the fan assembly become much better than the prior art. 
         [0028]    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.