Patent Publication Number: US-9903206-B2

Title: Impeller

Description:
FIELD OF THE INVENTION 
     The present invention relates to an impeller, and more particularly to an impeller of a fan. 
     BACKGROUND OF THE INVENTION 
     With increasing development of science and technology, the functions and operating speeds of various electronic devices or mechanical systems are gradually enhanced. For maintaining normal operations, a forced convection mechanism (e.g. a fan) is installed in the electronic device or the mechanical system to dissipate heat that is generated by the electronic components of the electronic device or the mechanical system and maintain normal operating temperature. In view of power-saving efficacy, various electronic devices should have enhanced operating efficiency if the power consumption is fixed. For example, it is important to provide a fan having enhanced working efficiency in a power-saving manner. 
       FIG. 1  is a schematic top view illustrating an impeller of a fan according to the prior art. The impeller  1  comprises a hub  10  and a plurality of blades  11 . The hub  10  is arranged at the center of the impeller  1 . The blades  11  are disposed around the outer periphery of the hub  10 . According to the practical requirements, the blades  11  have different profiles. For example, as shown in  FIG. 1 , the blades  11  are sweep-forward type blades. 
     As known, increasing the solidity of the blades  11  is a way of enhancing the working efficiency of the impeller  1 . In the impeller  1 , the ratio of the total area of the hub  10  and the blades  11  to the area of a circle whose radius R is from a center A to an outer periphery of the blades  11  is defined as the solidity. Moreover, for further increasing the working efficiency of the impeller  1 , the blades  11  should be uniformly distributed. Since the length of the connecting end  111  and the stagger angle of each blade  11  are restricted by the perimeter of the hub  10 , the number of blades  11  fails to be largely increased. Under this circumstance, the working efficiency of the impeller  1  is usually unsatisfactory. 
     Please refer to  FIG. 1  again. There is a spacing interval B between every two adjacent blades  11 . The spacing interval B between every two adjacent blades  11  at the outer peripheries of the blades  11  is wider than the spacing interval B between every two adjacent blades  11  near the hub  10 . Under this circumstance, the number of blades  11  fails to be further increased, and thus it is difficult to effectively increase the solidity. Moreover, if large blades  11  are used to increase the solidity, every two adjacent blades  11  possibly overlap with each other. In this situation, the complexity of designing the mold of the impeller  1  and the fabricating cost of the impeller increases, and the performance of the fan deteriorates. 
     SUMMARY OF THE INVENTION 
     The present invention provides an impeller having increased solidity of blades and an increased number of blades, thereby enhancing the operating efficiency thereof. 
     In accordance with an aspect of the present invention, there is provided an impeller. The impeller includes a hub and a plurality of blades. The blades are disposed around an outer periphery of the hub. Each of the blades includes a connecting end, a sweep-back part and a sweep-forward part. The connecting end is coupled with the hub. The sweep-back part is disposed at an edge of the blade and extended from the connecting end. An extending direction of the sweep-back part is opposed to a rotating direction of the impeller. The sweep-forward part is extended from the sweep-back part. An extending direction of the sweep-forward part is the same as the rotating direction of the impeller. 
     In an embodiment, the impeller is installed in an axial-flow fan. 
     In an embodiment, the sweep-back part and the sweep-forward part are arranged at a front edge of the blade. 
     In an embodiment, the front edge of the blade is a windward edge, and a rear edge of the blade is opposed to the front edge. 
     In an embodiment, the blade further includes another sweep-back part and another sweep-forward part, which are arranged at the rear edge of the blade. 
     In an embodiment, the sweep-forward part of a specified blade and the rear edge of a previous blade are substantially parallel with each other. 
     In an embodiment, the impeller is rotated with respect to a rotating axis, the blade has a centerline, a stagger angle is defined between the centerline and a plane perpendicular to the rotating axis, and the stagger angle ranges between 10 and 60 degrees. 
     In an embodiment, the hub has a center. A base point is located between the hub and the sweep-back part, a sweep-back terminal point is located between the sweep-back part and the sweep-forward part, and a sweep-forward terminal point is located at the end of the sweep-forward part. 
     In an embodiment, a sweep-back angle is formed between a first line defined by the center and the base point and a second line defined by the center and the sweep-back terminal point. In addition, a sweep-forward angle is formed between the second line and a third line defined by the center and the sweep-forward terminal point. 
     In an embodiment, the sweep-back angle ranges between −10 and −60 degrees with respect to the first line. 
     In an embodiment, the sweep-forward angle ranges between 10 and 60 degrees with respect to the second line. 
     In an embodiment, a first radius R 1  is defined from the center to the base point, a second radius R 2  is defined from the center to the sweep-back terminal point, a third radius R 3  is defined from the center to the outermost periphery of the blade, and a relationship between the R 1 , R 2 , and R 3  is: 0.1&lt;(R 2 −R 1 )/(R 3 −R 1 )&lt;0.35. 
     The above contents of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic top view illustrating an impeller of a fan according to the prior art; 
         FIG. 2A  is a schematic perspective view illustrating an impeller of an axial-flow fan according to an embodiment of the present invention; 
         FIG. 2B  is a schematic cross-sectional view illustrating a blade of the impeller of  FIG. 2A ; 
         FIG. 2C  is a schematic top view illustrating the impeller of  FIG. 2A ; and 
         FIG. 3  is a schematic plot illustrating the relationship between the airflow amount, the airflow pressure and the power consumption of the impeller of  FIG. 2A  in comparison with the impeller of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. 
       FIG. 2A  is a schematic perspective view illustrating an impeller of an axial-flow fan according to an embodiment of the present invention. The impeller  2  comprises a hub  20  and a plurality of blades  21 . The hub  20  is arranged at the center of the impeller  2 . The blades  21  are disposed around the outer periphery of the hub  20 . Each of the blades  21  has a connecting end  211  connected to the outer periphery of the hub  20 . In this embodiment, the impeller  2  is rotated in the counter-clockwise direction. The blade  21  has two sides. Upon rotation of the impeller  2 , the front edge  212  of the blade  21  is a windward edge, and the other edge of the blade  21  is a rear edge  213 . That is, the front edge  212  and the rear edge  213  are arranged at opposite sides of the blade  21 . The front edge  212  comprises a sweep-back part  212   a  and a sweep-forward part  212   b . The sweep-back part  212   a  is extended from the connecting end  211  in an extending direction opposed to the rotation direction of the impeller  2 . The sweep-forward part  212   b  is extended from the sweep-back part  212   a  in an extending direction the same as the rotation direction of the impeller  2 . In this embodiment, the sweep-back part  212   a  and the sweep-forward part  212   b  are formed on a single side (e.g. the front edge) of the blade  21 . Alternatively, in some embodiments, another sweep-back part and another sweep-forward part may be also formed on the other side (e.g. the rear edge) of the blade  21 . Meanwhile, both sides of the blade  21  have respective sweep-back parts and respective sweep-forward parts. 
       FIG. 2B  is a schematic cross-sectional view illustrating a blade of the impeller of  FIG. 2A . The Z axis (i.e. rotating axis) indicates the direction of the center bearing of the impeller  2 . That is, the impeller  2  is rotated with respect to the Z axis. The cross section of the blade  21  has a centerline L. A stagger angle D is defined between the centerline L and a plane S perpendicular to the rotating axis. As the stagger angle D is changed, the surface pressure distribution of the impeller  2  is changed, thereby adjusting the airflow amount passing through the impeller  2 . If the stagger angle D is too large, a problem of causing re-circulation of the airflow will possibly occur. Under this circumstance, the working efficiency of the impeller  2  is impaired. For maintaining good working efficiency, the stagger angle D ranges between 10 and 60 degrees. 
       FIG. 2C  is a schematic top view illustrating the impeller of  FIG. 2A . The hub  20  of the impeller  2  has a center A′. From the connecting end  211  to the sweep-forward part  212   b  through the sweep-back part  212   a , the blade  21  comprises a base point P 1 , a sweep-back terminal point P 2  and a sweep-forward terminal point P 3 . The base point P 1  is located between the hub  20  and the sweep-back part  212   a , the sweep-back terminal point P 2  is located between the sweep-back part  212   a  and the sweep-forward part  212   b , and the sweep-forward terminal point P 3  is located at the end of the sweep-forward part  212   b . Namely, the sweep-back part  212   a  is formed between the base point P 1  and the sweep-back terminal point P 2 , and the sweep-forward part  212   b  is formed between the sweep-back terminal point P 2  and the sweep-forward terminal point P 3 . A sweep-back angle D 1  is formed between a first line defined by the center A′ and the base point P 1  and a second line defined by the center A′ and the sweep-back terminal point P 2 . In addition, a sweep-forward angle D 2  is formed between the second line and a third line defined by the center A′ and the sweep-forward terminal point P 3 . In addition, a first radius R 1  is defined from the center A′ to the base point P 1 , a second radius R 2  is defined from the center A′ to the sweep-back terminal point P 2 , and a third radius R 3  is defined from the center A′ to the outermost periphery of the blade  21 . A relationship between the first radius R 1 , the second radius R 2  and the third radius R 3  is: 0.1&lt;(R 2 −R 1 )/(R 3 −R 1 )&lt;0.35. 
     In a case that the stagger angle D ranges between 10 and 60 degrees, the sweep-back angle D 1  ranges between −10 and −60 degrees with respect to the first line, and the sweep-forward angle D 2  ranges between 10 and 60 degrees with respect to the second line. Since the impeller  2  is designed according to the relationship between the first radius R 1 , the second radius R 2  and the third radius R 3 , the power consumption is reduced by about 10% if the airflow amount and the airflow pressure are fixed. 
     Please refer to  FIG. 2C  again. In the impeller  2  of the present invention, the sweep-back part  212   a  and the sweep-forward part  212   b  are arranged at the same edge of the blade  21 , and the sweep-forward part  212   b  is arranged behind the sweep-back part  212   a . Consequently, the rear edge  213  of a specified blade  21  and the front edge  212  of a next blade  21  are substantially identical parallel with each other. That is, the sweep-forward part  212   b  of a specified blade  21  and the rear edge  213  of a previous blade  21  are substantially parallel with each other. Since the number of blade  21  or the area of the blade  21  can be increased, the solidity is increased. Under this circumstance, the operating efficiency of the impeller  2  is enhanced. 
       FIG. 3  is a schematic plot illustrating the relationship between the airflow amount, the airflow pressure and the power consumption of the impeller of  FIG. 2A  in comparison with the impeller of  FIG. 1 . The solid curves indicate the relationships between the airflow amount and the airflow pressure of the impeller  2  of the present invention and the conventional impeller  1 . The dashed curves indicate the relationships between the airflow pressure and the power consumption of the impeller  2  of the present invention and the conventional impeller  1 . Assuming that the airflow amount is 140 CFM (ft3/min), the power consumption of the impeller  2  is obviously lower than the power consumption of the conventional impeller  1 . That is, since the power consumption of the impeller  2  of the present invention is reduced, the power-saving purpose is achieved. 
     From the above description, the impeller of the present invention comprises a plurality of blades. Each of the blades comprises a connecting end, a sweep-back part and a sweep-forward part. The sweep-back part is extended from the connecting end. The sweep-forward part is extended from the sweep-back part. The sweep-back part and the sweep-forward part define a front edge of the blade. Since the sweep-forward part is arranged behind the sweep-back part, the number of blades can be increased but every two adjacent blades are not overlapped with each other. In this situation, the solidity of the plurality of blades will be increased, and thus the operating efficiency of the impeller is enhanced. That is, in the condition that the airflow amount and the airflow pressure are identical, the power consumption of the impeller of the present invention is largely reduced when compared with the conventional impeller. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.