Patent Publication Number: US-8113775-B2

Title: Axial flow fan

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an axial flow fan. 
     2. Description of the Related Art 
       FIG. 1  is a perspective view of a conventional axial flow fan  10 . The axial flow fan  10  includes an outer frame  101 , a plurality of stator vanes  102 , and a base  103 . The outer frame  101  is a hollow member provided with an intake vent and an exhaust vent. There is formed a diameter expanded part  101   a  and there are disposed the stator vanes  102  and the base  103  at the exhaust vent of the outer frame  101 . The outer frame  101 , the stator vanes  102 , and the base  103  are integrally formed by injection molded resin. 
     In injection molding, one die is formed by combining two kinds of die parts, namely, a fixed die part and a movable die part. Melt resin is cast into the die and then is cooled. Thereafter, the cooled and solidified resin is taken out of the die. The outer frame  101 , the stator vanes  102 , and the base  103  are thereby formed as one member. 
     There are provided a plurality of seats  104  formed at parts where the diameter expanded part  101   a  and the stator vanes  102  are respectively joined. The seats  104  are positioned at blind portions when an integrally molded component having the outer frame  101 , the stator vanes  102 , and the base  103  is seen from a direction of being taken out of the die. When air is exhausted from the exhaust vent and hits the seats  104 , there arise problems of noise generation, as well as decreases in volume of airflow and static pressure thereof. 
     SUMMARY OF THE INVENTION 
     The present invention provides an axial flow fan including an impeller that has a plurality of rotor vanes and is rotatable about a central axis, a motor that rotary drives the impeller, a base portion that supports the motor, a housing that has an intake vent, an exhaust vent, and an inner peripheral surface to surround the impeller and the motor, and a plurality of stator vanes that respectively connects the base portion and the housing, wherein the inner peripheral surface has a first inner peripheral surface formed to increase a distance from the central axis toward the intake vent or the exhaust vent in an axial direction, and there is formed a recess between the first inner peripheral surface and a stator vane that is included in the plurality of stator vanes and faces the first inner peripheral surface. 
     According to the above described configuration, airflow is allowed to smoothly pass through the housing, resulting in a decrease in noise generated in the axial flow fan. Moreover, decreases can be prevented in a volume of airflow taken into or exhausted from the axial flow fan as well as a static pressure thereof. Further, the housing can be molded with a smaller amount of resin, thereby realizing reduction in cost for manufacture of the axial flow fan. 
     Other features, elements, advantages and characteristics of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a conventional axial flow fan. 
         FIG. 2  is a perspective view of an axial flow fan according to a first preferred embodiment of the present invention. 
         FIG. 3  is a plan view of the axial flow fan shown in  FIG. 2 , which is seen from an exhaust side thereof. 
         FIG. 4  is a cross sectional view of the axial flow fan shown in  FIG. 2 . 
         FIG. 5  is a cross sectional view of an axial flow fan according to a first preferred modification of the present invention. 
         FIG. 6  is a cross sectional view of an axial flow fan according to a second preferred modification of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring to  FIGS. 2 through 6 , preferred embodiments of the present invention will be described in detail. It should be noted that in the explanation of the present invention, when positional relationships among and orientations of the different components are described as being up/down or left/right, ultimately positional relationships and orientations that are in the drawings are indicated; positional relationships among and orientations of the components once having been assembled into an actual device are not indicated. Meanwhile, in the following description, an axial direction indicates a direction parallel to a rotation axis, and a radial direction indicates a direction perpendicular to the rotation axis. 
       FIGS. 2 ,  3 , and  4  are respectively a perspective view, a plan view, and a cross sectional view of an axial flow fan  11  according to a first preferred embodiment of the present invention. 
     As shown in  FIGS. 2 ,  3 , and  4 , the axial flow fan  11  preferably includes an impeller  12 , a plurality of stator vanes  13 , a motor portion  14 , and a housing  18 . The impeller  12  is preferably rotary driven about a central axis  23  by the motor portion  14 . The housing  18  is preferably a hollow member provided with an exhaust vent  41  and an intake vent  43 . The stator vanes  13  are preferably disposed at the exhaust vent  41 , and are formed integrally with the housing  18  by injection molded resin. Alternatively, the stator vanes  13  and the housing  18  may be integrally formed by aluminum die-casting. 
     As shown in  FIG. 4 , the impeller  12  preferably includes a cup  21  in a capped and substantially cylindrical shape, and a plurality of rotor vanes  22 . The rotor vanes  22  are preferably disposed on an outer peripheral surface of a cylindrical wall of the cup  21  so as to be equally spaced apart from each other in a circumferential direction around the central axis  23 . There is preferably fixed a rotor holder  121  to an inner side of the cup  21 . The rotor holder  121  is preferably a capped and substantially cylindrical member made of a magnetic material (such as a metal material). The rotor holder  121  preferably includes a cylindrical inner peripheral surface to which a rotor magnet  31  in a substantially annular shape is fixed. There is fixed by press fitting or the like to a capped part of the rotor holder  121  a shaft  123  having a substantially columnar shape. 
     As shown in  FIG. 4 , the motor portion  14  is preferably disposed in the impeller  12  and includes a stator  141  (partially shown) and a circuit board (not shown). The stator  141  radially preferably faces the rotor magnet  31  and is electrically connected to the circuit board. The circuit board and the stator  141  preferably receive electric currents and control signals transmitted from an external power supply (not shown) through a plurality of lead wires (not shown). When the stator  141  is supplied with an electric current, there is generated a magnetic field at the stator  141 . Interaction between the magnetic field generated at the stator  141  and a magnetic field of the rotor magnet  31  causes torque between the stator  141  and the rotor magnet  31 . Such torque preferably rotary drives the impeller  12  about the central axis  23  to cause airflow along the central axis  23 . It should be noted that, in  FIG. 4 , air flows from the axially upper side to the axially lower side (namely, from the intake vent  43  to the exhaust vent  41 ). 
     As shown in  FIGS. 2 ,  3 , and  4 , the housing  18  has an outer frame  15  and a base portion  16 . The outer frame  15  is preferably a hollow member in a substantially square pole shape. In planar view, the outer frame  15  preferably includes a substantially rectangular outline and an inner peripheral surface  40  in a substantially circular shape. 
     The inner peripheral surface  40  preferably includes intake-side first inner peripheral surfaces  42   a  respectively formed at four corners thereof of the intake vent  43 . The intake-side first inner peripheral surfaces  42   a  preferably are formed so as to gradually increase the radial distance between the central axis  23  and the inner peripheral surface  40  toward the intake vent  43  in the axial direction. Similarly, the inner peripheral surface  40  preferably includes exhaust-side first inner peripheral surfaces  42   b  respectively formed at four corners thereof of the exhaust vent  41  so as to gradually increase the radial distance between the central axis  23  and the inner peripheral surface  40  toward the exhaust vent  41  in the axial direction. 
     As shown in  FIG. 4 , the inner peripheral surface  40  preferably includes a second inner peripheral surface  45  formed to be substantially in parallel with the central axis  23 . The second inner peripheral surface  45  and the respective first inner peripheral surfaces  42  preferably are smoothly continued to each other. 
     The base portion  16  is preferably a bottomed and substantially cylindrical member and axially supports the motor portion  14 . The base portion  16  is preferably disposed in the outer frame  15  at the intake vent  43  in the axial direction. The base portion  16  preferably includes a surface, on the axially exhaust side, which is flush with respect to ends  15   a  of the outer frame  15  on the axially exhaust side. 
     As shown in  FIGS. 2 ,  3 , and  4 , the stator vanes  13  are preferably disposed between the inner peripheral surface  40  of the outer frame  15  and the outer peripheral surface of the base portion  16  so as to be equally spaced apart from each other in the circumferential direction, thereby serving as connectors between the inner peripheral surface  40  and the base portion  16 . Each of the stator vanes  13  preferably includes a first edge  25 , a second edge  26 , a first surface  27 , and a second surface  28 . The first surface  27  and the second surface  28  are preferably inclined with respect to the central axis  23 , and the first edge  25  is positioned on the intake side in the axial direction while the second edge  26  is positioned on the exhaust side thereof. The first edge  25  is preferably formed to be positioned on the opposite side with respect to the second edge  26  in a direction R of rotation of the impeller  12 . The first surface  27  is preferably oriented opposite to the direction R of rotation of the impeller  12  so as to mainly receive airflow which is generated by rotation of the impeller  12 . It should be noted that the impeller  12  is rotated in the direction R of rotation clockwise about the central axis  23 , as shown in  FIG. 2 . Further, each of the stator vanes  13  preferably includes an axial cross section in a vane shape with curved surfaces. According to such a configuration, an air circulative component generated by rotation of the impeller  12  is transformed to a component flowing along the central axis  23 , resulting in an increase in static pressure of air. 
     Alternatively, the first and second surfaces  27  and  28  may be made inclined with respect to the central axis  23  at a different angle, so that airflow is oriented to an arbitrary direction (such as the radially outward direction). The stator vanes  13  may be disposed not at the exhaust vent  41  but at the intake vent  43  in the axial direction. In this case, the second edge  26  is positioned on the opposite side with respect to the first edge  25  in the direction R of rotation of the impeller  12 . Air is oriented by the stator vanes  13  and is taken into the housing  18 . Accordingly, reduced is noise generated by airflow hitting the inner peripheral surface  40  and the like. 
     As shown in  FIGS. 2 ,  3 , and  4 , the plurality of stator vanes  13  preferably include a plurality of stator vanes  13 A each of which extends from the central axis  23  toward the corresponding exhaust-side first inner peripheral surface  42   b . There is formed a recess  52  at a part where a first outer edge  53  of each of the stator vanes  13 A is connected to the corresponding exhaust-side first inner peripheral surface  42   b . The recess  52  is preferably a space surrounded by the first outer edge  53  and the corresponding exhaust-side first inner peripheral surface  42   b . In other words, an end of the first outer edge  53  on the axially exhaust side radially faces the corresponding exhaust-side first inner peripheral surface  42   b  with the recess  52  interposed therebetween. On the other hand, an end of the first outer edge  53  on the axially intake side is connected to the second inner peripheral surface  45 . 
     Such a configuration minimizes a volume of each of the seats which is formed at a connection between the first outer edge  53  and the corresponding exhaust-side first inner peripheral surface  42   b . Therefore, airflow generated by rotation of the impeller  12  is allowed to smoothly pass in the vicinity of the respective connections. As a result, reduced is noise generated by airflow hitting the connections. 
     In addition, as the volume of each of the seats is minimized, there is secured a space to arrange therein the impeller  12  within the housing  18 , thereby realizing increases in volume of airflow and static pressure thereof. 
     The volume of each of the seats, which is minimized, enables reduction in the amount of resin required for forming of the housing  18  (the amount of aluminum, aluminum alloy, or the like in the case of aluminum die-casting). Therefore, reduction is realized in the cost of the material for the axial flow fan  11 . 
     The end of the first outer edge  53  on the axially intake side is preferably connected to a part  42   c  having a minimized diameter on the exhaust-side first inner peripheral surface  42   b  (more specifically, the end of the second inner peripheral surface  45  on the axially exhaust side). Accordingly, secured are strength of the connection between each of the stator vanes  13 A and the inner peripheral surface  40  as well as an inner diameter of the second inner peripheral surface  45 . It should be noted that each of the stator vanes  13 A may be connected to both the corresponding exhaust-side first inner peripheral surface  42   b  and the second inner peripheral surface  45  including the boundary therebetween. Further, the second edges  26  of the stator vanes  13  are formed to be flush with respect to the ends  15   a  of the outer frame  15 , thereby realizing prevention of an increase in size of the outer frame  15 . 
     Described below is an axial flow fan  11 A according to a first preferred modification made to the first preferred embodiment of the present invention.  FIG. 5  is a cross sectional view of the axial flow fan  11 A. The element of the axial flow fan  11 A identical to that of the axial flow fan  11  is denoted by the similar reference symbol, and description thereof will omitted. 
     As shown in  FIG. 5 , the axial flow fan  11 A preferably includes a plurality of stator vanes  13 B which are connected to the respective first inner peripheral surfaces  42 . Similarly to the stator vanes  13 A, the stator vanes  13 B are preferably disposed between the base portion  16  and the inner peripheral surface  40  so as to be equally spaced apart from each other in the circumferential direction. 
     There is formed a recess  52 A on the axially exhaust side of a radially outer end of each of the stator vanes  13 B. The recess  52 A is preferably a space surrounded by a first outer edge  53  which is substantially in parallel with the central axis  23 , a second outer edge  531  which is substantially perpendicular to the first outer edge  53 , and an exhaust-side first inner peripheral surface  42   b . On the other hand, the radially outer end of each of the stator vanes  13 B is preferably connected on the axially intake side thereof to the corresponding exhaust-side first inner peripheral surface  42   b . Both the recess  52 A and the end of the stator vane  13 B on the axially intake side are preferably overlapped with the corresponding first inner peripheral surface  42  when the recess  52 A is seen in the axial direction. According to such a configuration, the volume of the seat formed at the connection between the stator vane  13 B and the inner peripheral surface  40  is minimized. As a result, reduced is noise generated by airflow hitting the respective connections, and prevented are decreases in volume of airflow and static pressure thereof. 
     Each of the stator vanes  13 B preferably includes an end  13   a , on the axially exhaust side, which is flush with respect to the ends  15   a  of the outer frame  15 . According to such a configuration, the axial dimension of the axial flow fan  11 A is suppressed to realize reduction in size of the axial flow fan  11 A. 
     Each of the stator vanes  13 B preferably includes an end  13   b , on the axially intake side, which is flush with respect to parts (the boundaries between the second inner peripheral surface  45  and the respective exhaust-side first inner peripheral surfaces  42   b ) having a minimized diameter on the exhaust-side first inner peripheral surfaces  42   b . According to such a configuration, there is secured an adequate space for disposing the impeller  12  in the housing  18 . Airflow generated by rotation of the impeller  12  is guided smoothly to the stator vanes  13 , and reduced is noise generated by airflow hitting the stator vanes  13 B. It should be noted that the radially outer end of each of the stator vanes  13 B may be connected to both the second inner peripheral surface  45  and the corresponding first inner peripheral surface  42  including the boundary therebetween. 
     The first outer edge  53  and the second outer edge  531  may not necessarily form an angle equal to 90 degrees, but may form an acute angle or an obtuse angle. Further alternatively, the respective stator vanes  13 B may have such angles different from one another. 
       FIG. 6  is a cross sectional view of an axial flow fan  11 B according to a second preferred modification made to the first preferred embodiment of the present invention. The constituent of the axial flow fan  11 B identical to that of the axial flow fan  11  or  11 A is denoted by the identical reference symbol, and description thereof will be omitted. 
     As shown in  FIG. 6 , the axial flow fan  11 B preferably includes a plurality of stator vanes  13 C which are connected to the respective exhaust-side first inner peripheral surfaces  42   b . A radially outer end of each of the stator vanes  13 C is preferably connected on the axially intake side thereof to the corresponding exhaust-side first inner peripheral surface  42   b . On the other hand, there is formed a recess  52 B at the radially outer end of the stator vane  13 C on the axially exhaust side. The recess  52 B and the end of the stator vane  13 C on the axially intake side are preferably overlapped with the corresponding exhaust-side first inner peripheral surface  42   b  when the recess  52 B is seen in the axial direction. 
     As illustrated in  FIG. 6 , a boundary  54  between the first outer edge  53  and the end  13   a  on the axially exhaust side is preferably chamfered. Similarly, a boundary  541  between the first outer edge  53  and the second outer edge  531  is chamfered. Such a configuration reduces as much as possible the volume of the seat formed at a boundary between the stator vane  13 C and the corresponding exhaust-side first inner peripheral surface  42   b . As a result, airflow is allowed to smoothly pass in the vicinity of the boundary  54  and the boundary  541  of each of the stator vanes  13 C. Alternatively, the boundary  54  or  541  may be formed as a surface in a C-letter shape. 
     The first outer edge  53  may be positioned radially inside or outside the second inner peripheral surface  45 . The boundary  54  or  541  may be chamfered into a shape different from one another in the respective recesses  52 B or the respective stator vanes  13 C. 
     Alternatively, the stator vanes  13 A,  13 B, and  13 C according to the present invention may be provided on the axially intake side (that is, at the intake vent  43 ). The axial flow fan may include more than one type of stator vanes selected from the stator vanes  13 A,  13 B, and  13 C according to the present invention. Further, the radially outer end of each of the stator vanes  13 A,  13 B, and  13 C may be connected to a part other than the exhaust-side first inner peripheral surface  42   b . Even in such cases, airflow is allowed to smoothly pass in the vicinity of the respective stator vanes. 
     The intake-side first inner peripheral surfaces  42   a  may have a shape different from that of the exhaust-side first inner peripheral surfaces  42   b . Further, the respective intake-side first inner peripheral surfaces  42   a  (or the respective exhaust-side first inner peripheral surfaces  42   b ) may have shapes different from one another at the respective corners, and may have distances from the central axis  23  different from one another. 
     While the preferred embodiment and the preferred modifications of the present invention have been described above, the present invention is not limited to the above cases. It is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.