Patent Publication Number: US-11396880-B2

Title: Inline axial flow fan

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority under 35 U.S.C. § 119 to Japanese Application No. 2018-210792 filed on Nov. 8, 2018 the entire contents of which are hereby incorporated herein by reference. 
     1. FIELD OF THE INVENTION 
     The present disclosure relates to an inline axial flow fan. 
     2. BACKGROUND 
     Conventionally, an inline axial flow fan has been known in which two axial air blow units are connected in series along a predetermined central axis. 
     SUMMARY 
     According to one example embodiment of the present disclosure, an inline axial flow fan includes a first fan including a first impeller that is rotatable about a central axis, a first motor portion that rotates the first impeller, and a first case that surrounds an outer periphery of the first impeller, and a second fan including a second impeller that is rotated about a central axis, a second motor portion that rotates the second impeller, and a second case that surrounds an outer periphery of the second impeller, the first fan and the second fan being positioned in sequence from one axial side to another axial side. The first case includes multiple first slits located radially outward of the first impeller. The second case includes multiple second slits located radially outward of the second impeller. The inline axial flow fan includes a flange extending radially outward from an outer peripheral surface of the first case or the second case located between the first slit and the second slit in the axial direction. 
     The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view including a partial cross section showing an inline axial flow fan of an example embodiment of the present disclosure. 
         FIG. 2  is a side view including a partial cross section of the inline axial flow fan of an example embodiment of the present disclosure. 
         FIG. 3  is a cross-sectional view of the inline axial flow fan of an example embodiment of the present disclosure. 
         FIG. 4  is a cross-sectional view taken along line IV-IV of  FIG. 3 . 
         FIG. 5  is a cross-sectional view of an inline axial flow fan of a modification of an example embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In each of the drawings, the Z-axis direction is a vertical direction in which the positive side is the upper side and the negative side is the lower side. The axial direction of a central axis J, which is a virtual axis appropriately shown in each drawing, is parallel to the Z-axis direction, that is, the vertical direction. In the following description, if not explicitly stated otherwise, a direction parallel to the axial direction of the central axis J is simply referred to as “axial direction”, a radial direction centered on the central axis J is simply referred to as “radial direction”, and a circumferential direction centered on the central axis J is simply referred to as “circumferential direction”. 
     In the example embodiment, the lower side corresponds to one axial side and the upper side corresponds to the other axial side. Note that the upper side and the lower side are simply terms for explaining the relative positional relationship among the parts, and the actual positional relationship and the like may be a positional relationship or the like referred to by different terms. 
       FIG. 1  is a perspective view including a partial cross section showing an inline axial flow fan of the example embodiment.  FIG. 2  is a side view including a partial cross section of the inline axial flow fan of the example embodiment.  FIG. 3  is a cross-sectional view of the inline axial flow fan of the example embodiment. 
     An inline axial flow fan  100  of the example embodiment is used as a blower of an air cleaner, for example. 
     As shown in  FIG. 1 , the inline axial flow fan  100  includes a first fan  10 , a second fan  20 , a flange  30 , and a housing  50 . The housing  50  is a rectangular tube-shaped casing that is open to upper and lower sides. The first fan  10  is accommodated in a lower part of the housing  50 . The second fan  20  is accommodated in an upper part of the housing  50 . The first fan  10  and the second fan  20  are disposed in sequence along the axial direction from one axial side to the other axial side. The flange  30  is a plate-like member that extends radially outward from an intermediate position in the axial direction between the first fan  10  and the second fan  20  inside the housing  50 . 
     The inline axial flow fan  100  sucks in air from a lower surface of the housing  50  and injects the air from an upper surface of the housing  50 . In the inline axial flow fan  100 , the first fan  10  is disposed on the intake side, and the second fan  20  is disposed on the exhaust side. 
     As illustrated in  FIGS. 2 and 3 , the first fan  10  includes a first impeller  10 A, a first motor portion  11 , a first case  12 , and multiple first support ribs  13 . 
     The first impeller  10 A has multiple first blades  10   a  disposed radially at a constant pitch around the central axis J. The first impeller  10 A is rotated about the central axis J in a predetermined direction by the first motor portion  11 . While the number of first blades  10   a  in the first impeller  10 A is seven in the example embodiment, this can be changed according to the design of the inline axial flow fan  100 . 
     The first case  12  is a cylindrical casing that surrounds the radially outer side of the first impeller  10 A. The first case  12  is made of resin or metal, for example. The first case  12  includes a cylindrical peripheral wall portion  12 A extending in the axial direction, and multiple first slits  12 B penetrating the peripheral wall portion  12 A in the radial direction. 
     Each of the first slits  12 B extends in a direction intersecting the central axis J when viewed from the radial direction. The longitudinal direction of the first slit  12 B intersects the ridgeline of the outer peripheral edge in the radial direction of the first blade  10   a  at an angle of approximately 90 degrees. The multiple first slits  12 B extend in directions parallel to one another. The multiple first slits  12 B are arranged at regular intervals in a region that is one lap in the circumferential direction of the peripheral wall portion  12 A. 
     The first case  12  forms a passage of an airflow F by an inner peripheral surface of the peripheral wall portion  12 A. In the case of the example embodiment, a lower end portion of the peripheral wall portion  12 A that is the intake side of the first fan  10  has a shape that expands radially toward the lower side. In the peripheral wall portion  12 A, the part accommodating the first impeller  10 A and above is cylindrical. 
     Multiple first support ribs  13  are disposed in an upper opening of the peripheral wall portion  12 A. The first fan  10  of the example embodiment has four first support ribs  13 . The multiple first support ribs  13  extend radially about the central axis J. A radially outer end portion of the first support rib  13  is connected to the inner peripheral surface of the peripheral wall portion  12 A. A radially inner end portion of the first support rib  13  is connected to a motor support portion  13 A that supports the first motor portion  11 . 
     As shown in  FIG. 3 , the first motor portion  11  is attached to a lower surface of the motor support portion  13 A. In the example embodiment, the first motor portion  11  is an inner rotor type motor. The first motor portion  11  has a shaft  11 A centered on the central axis J. The shaft  11 A extends downward from a motor case  11 B of the first motor portion  11 . The first impeller  10 A is fixed to a lower end portion of the shaft  11 A. The first motor portion  11  may be an outer rotor type motor. 
     The second fan  20  includes a second impeller  20 A, a second motor portion  21 , a second case  22 , and multiple second support ribs  23 . 
     The second impeller  20 A has multiple second blades  20   a  disposed radially at a constant pitch around the central axis J. The second impeller  20 A is rotated about the central axis J in the same direction as that of the first impeller  10 A by the second motor portion  21 . As a result, the second impeller  20 A generates an airflow in the same direction as that of the airflow generated by the first impeller  10 A. That is, both the first impeller  10 A and the second impeller  20 A cause an airflow from the lower side to the upper side. While the number of second blades  20   a  in the second impeller  20 A is five in this example embodiment, this can be changed according to the design of the inline axial flow fan  100 . 
     The second case  22  surrounds the radially outer side of the second impeller  20 A. The second case  22  has a cylindrical peripheral wall portion  22 A extending in the axial direction, and multiple second slits  22 B penetrating the peripheral wall portion  22 A in the radial direction. 
     Each of the second slits  22 B extends in a direction intersecting the central axis J when viewed from the radial direction. The longitudinal direction of the second slit  22 B intersects the ridgeline of the outer peripheral edge in the radial direction of the second blade  20   a  at an angle of approximately 90 degrees. The multiple second slits  22 B extend in directions parallel to one another. The multiple second slits  22 B are arranged at regular intervals in a region that is one lap in the circumferential direction of the peripheral wall portion  22 A. 
     The second case  22  forms a passage of the airflow F by an inner peripheral surface of the peripheral wall portion  22 A. In the case of the example embodiment, an upper end portion of the peripheral wall portion  22 A that is the exhaust side of the second fan  20  has a shape that expands radially toward the upper side. In the peripheral wall portion  22 A, the portion accommodating the second impeller  20 A and below is cylindrical. 
     Multiple second support ribs  23  are disposed in a lower opening of the peripheral wall portion  22 A. The second fan  20  of the example embodiment has four second support ribs  23 . The multiple second support ribs  23  extend radially about the central axis J. A radially outer end portion of the second support rib  23  is connected to the inner peripheral surface of the peripheral wall portion  22 A. A radially inner end portion of the second support rib  23  is connected to a motor support portion  23 A that supports the second motor portion  21 . 
     The second motor portion  21  is attached to an upper surface of the motor support portion  23 A. In the example embodiment, the second motor portion  21  is an inner rotor type motor. The second motor portion  21  has a shaft  21 A centered on the central axis J. The shaft  21 A extends upward from a motor case  21 B of the second motor portion  21 . The second impeller  20 A is fixed to an upper end portion of the shaft  21 A. The second motor portion  21  may be an outer rotor type motor. 
     As shown in  FIG. 3 , the first fan  10  and the second fan  20  are disposed next to one another in the axial direction with the upper opening of the peripheral wall portion  12 A and the lower opening of the peripheral wall portion  22 A abutting each other. The inner diameter of the peripheral wall portion  12 A and the inner diameter of the peripheral wall portion  22 A are the same, and the peripheral wall portion  12 A and the peripheral wall portion  22 A form one passage that is continuous in the axial direction. 
     The motor support portion  13 A of the first fan  10  and the motor support portion  23 A of the second fan  20  are disposed so as to overlap one another in axial view. The multiple first support ribs  13  of the first fan  10  and the multiple second support ribs  23  of the second fan  20  are disposed so as to overlap at least partially in axial view. Air flows in the axial direction through a gap between the first support ribs  13  adjacent in the circumferential direction and a gap between the second support ribs  23  adjacent in the circumferential direction. 
     The housing  50  has a rectangular tube-shaped main body portion  51  having a bottom wall portion  51   a  and extending in the vertical direction, an upper lid portion  52  attached to the upper side of the main body portion  51 , and an air filter  53  attached to the lower side of the main body portion  51 . 
     The main body portion  51  has a first opening  50 A open to the lower side and a second opening  50 B open to the upper side. That is, the housing  50  has the first opening  50 A on one axial side and the second opening  50 B on the other axial side, and the air filter  53  is attached to the first opening  50 A. By providing the air filter  53  and the main body portion  51 , it is possible to prevent entry of wind that has not passed through the air filter  53 . As a result, the inline axial flow fan  100  can be easily used as a blower for an air cleaner. Note that when the airflow F of the inline axial flow fan  100  is headed downward, the air filter  53  is attached to the upper second opening  50 B. 
     The first fan  10  and the second fan  20  are accommodated in the main body portion  51  of the housing  50 . As shown in  FIGS. 1 to 3 , the flat plate-like flange  30  that extends radially outward from the outer peripheral surface of the first case  12  is disposed at an intermediate position in the axial direction between the first fan  10  and the second fan  20 . 
     The flange  30  is a rectangular plate material having a circular through hole that penetrates the flange  30  in the axial direction. An inner peripheral surface of the flange  30  is in contact with the outer peripheral surface of the first case  12 . An outer peripheral surface of the flange  30  is in contact with the inner peripheral surface of the main body portion  51 . The flange  30  divides, into upper and lower parts, a space surrounded by the inner peripheral surface of the housing  50 , and the first case  12  and the second case  22 . 
     In the example embodiment, the flange  30  only needs to be a member that inhibits air flow in the axial direction, and the inner peripheral end and the outer peripheral end of the flange  30  do not necessarily have to be sealed. A slight gap can be formed between an end surface on the inner peripheral side of the flange  30  and the outer peripheral surface of the first case  12 , and a slight gap can be formed between an end surface on the outer peripheral side of the flange  30  and the inner peripheral surface of the housing  50 . That is, the flange  30  may be configured to partition the space between the first case  12  and the second case  22  and the housing  50  in the axial direction. 
     While the flange  30  is disposed on the outer peripheral surface of the first case  12  in the example embodiment, the axial position of the flange  30  can be changed. The axial position of the flange  30  can be changed within a range between the upper end of the first slit  12 B and the lower end of the second slit  22 B. Additionally, multiple flanges  30  may be provided within the above range. 
     Additionally, the flange  30  may be a member united with the first case  12  or the second case  22 . The flange  30  may be a member integrated with the main body portion  51  of the housing  50 . The flange  30  may be divided into multiple plate members in the circumferential direction. 
     The height of the main body portion  51  of the housing  50  coincides with the height of the first fan  10  and the second fan  20  stacked in the axial direction. The lower end of the peripheral wall portion  12 A of the first fan  10  is in contact with an upper surface of the bottom wall portion  51   a . This suppresses air flow in the radial direction between the inside of the housing  50  and the lower opening of the first fan  10 . With this configuration, the inline axial flow fan  100  has a space  100 A surrounded by the first case  12 , the housing  50 , and the flange  30 , as shown in  FIGS. 1 to 3 . 
     The axial position of the upper opening of the second fan  20  coincides with the axial position of the upper opening of the main body portion  51 . The upper lid portion  52  is attached to the second opening  50 B of the housing  50 . A lower surface of the upper lid portion  52  is in contact with the upper end of the peripheral wall portion  22 A of the second fan  20  and the upper end of the main body portion  51 . This suppresses airflow in the radial direction between the inside of the housing  50 , and the upper opening of the second fan  20  and the upper opening of the main body portion  51 . With this configuration, the inline axial flow fan  100  has a space  100 B surrounded by the second case  22 , the housing  50 , and the flange  30 , as shown in  FIGS. 1 to 3 . 
     The upper lid portion  52  has a mesh portion  52   a  in a region located inside the opening of the second fan  20  in axial view. The mesh portion  52   a  has many through holes axially penetrating the upper lid portion  52 . The mesh portion  52   a  functions as a finger guard for preventing insertion of fingers into the second fan  20  from the second opening  50 B. 
     In the inline axial flow fan  100  of the example embodiment, the first case  12  has the first slits  12 B, and the second case  22  has the second slits  22 B. With this configuration, during operation of the first fan  10  and the second fan  20 , air can be taken in and out of the spaces  100 A and  100 B and the inside of the first case  12  and the second case  22  through the first slits  12 B and the second slits  22 B. That is, the air outside the first case  12  and the second case  22  can be used as a pressure buffer in the respective wind tunnels of the first fan  10  and the second fan  20 . As a result, in each of the first fan  10  and the second fan  20 , the pressure inside the wind tunnel is easily maintained within an appropriate range. Hence, it is possible to suppress generation of noise due to pressure fluctuation inside the wind tunnel. 
     Additionally, the flange  30  divides the space between the first case  12  and the second case  22  and the housing  50  into the two spaces  100 A and  100 B in the axial direction. Accordingly, in the second fan  20  on the exhaust side, air discharged to the space  100 B from the second slits  22 B is not sucked into the wind tunnel from the first slits  12 B of the first fan  10  on the intake side. When the air discharged from the second slits  22 B is sucked in from the first slits  12 B, circulating air that does not contribute to the airflow F of the inline axial flow fan  100  is generated in the housing  50 , and the static pressure of the inline axial flow fan  100  decreases. By providing the flange  30  in the inline axial flow fan  100 , it is possible to suppress decrease in static pressure due to the provision of the first slits  12 B and the second slits  22 B. Hence, according to the example embodiment, the inline axial flow fan  100  that achieves both low noise and high static pressure is provided. 
     In the example embodiment, the housing  50  has a rectangular tube shape extending in the axial direction, and the first case  12  and the second case  22  are cylindrical at least in a part from the first slits  12 B to the second slits  22 B in the axial direction. According to this configuration, an inline axial flow fan with higher static pressure can be obtained. Hereinafter, a description will be given with reference to  FIG. 4 . 
       FIG. 4  is a cross-sectional view taken along line IV-IV shown in  FIG. 3 . 
     As shown in  FIG. 4 , the radial gap between the cylindrical second case  22  and the rectangular tube-shaped main body portion  51  is wide at the corner of the main body portion  51  and narrow at the center of the sidewall of the main body portion  51 . The position where the outer peripheral surface of the second case  22  and the inner peripheral surface of the main body portion  51  come closest is a narrow portion  105  where the air passage in the circumferential direction becomes narrow. In the inline axial flow fan  100  of the example embodiment, the space  100 B has narrow portions  105  at four locations in the circumferential direction. 
     While the airflow between the space  100 A and the space  100 B is suppressed by the flange  30 , the space  100 B is circumferentially connected over one lap on the outer side of the second case  22 . Hence, an airflow occurs in the circumferential direction in the space  100 B. When air flows in a wide range in the circumferential direction outside the second case  22 , the air discharged from some of the second slits  22 B flows around the outside of the second case  22  in the circumferential direction, whereby circulating air flowing into the second case  22  from the other second slits  22 B occurs. Such circulating air is not used as the airflow F of the inline axial flow fan  100 , and therefore causes reduction in the static pressure characteristics of the inline axial flow fan  100 . 
     In the example embodiment, narrow portions  105  are provided in multiple locations in the circumferential direction of the space  100 B in order to suppress the circulating air in the circumferential direction. The space  100 B is partitioned into four spaces  101 ,  102 ,  103 , and  104  in the circumferential direction by four narrow portions  105 . As a result, for example, the circumferential flow of air discharged into the space  101  from the second slits  22 B is inhibited by the narrow portion  105 , hardly flows into the adjacent space  102  or space  104 , and is sucked into the wind tunnel from the second slits  22 B in the vicinity of the narrow portion  105 . 
     As described above, in the inline axial flow fan  100  of the example embodiment, since air is circulated in the four spaces  101  to  104  partitioned in the circumferential direction outside the second case  22 , it is possible to suppress generation of circulating air flowing in the circumferential direction outside the second case  22 . Hence, according to the example embodiment, a high static pressure inline axial flow fan  100  is obtained. 
     Note that while the operational effect of the narrow portion  105  in the space  100 B on the second fan  20  side has been described in the above description, the same operational effect can also be obtained in the space  100 A on the first fan  10  side. The second case  22  and the main body portion  51  may be in contact with each other in the narrow portion  105 . 
     The inventor has verified the noise reduction by the configuration of the example embodiment. It has been confirmed that as compared with an inline axial flow fan having a conventional configuration that does not include the first slits  12 B, the second slits  22 B, and the flange  30 , the inline axial flow fan  100  of the example embodiment can achieve noise reduction of not less than 1.5 dB under conditions with which an equivalent air volume can be obtained. 
     While the first fan  10 , the second fan  20 , and the flange  30  are accommodated in the housing  50  in the configuration of the above example embodiment, the inline axial flow fan  100  may be configured not to include the housing  50 . Even in this case, the flange  30  is disposed between a space radially outward of the first case  12  and a space radially outward of the second case  22  in the axial direction. Hence, it is possible to restrain the air discharged from the second slits  22 B from flowing into the first case  12  from the first slits  12 B. As a result, noise of the inline axial flow fan  100  can be reduced. 
     In the inline axial flow fan  100 , one of the first impeller  10 A and the second impeller  20 A may be replaced with an impeller having an opposite air blowing direction to form a counter-rotating fan that rotates the first impeller  10 A and the second impeller  20 A in opposite directions. By using a counter-rotating fan, it is possible to achieve a higher static pressure and a larger air volume than an inline axial flow fan in which two impellers rotate in the same direction. 
       FIG. 5  is a cross-sectional view of an inline axial flow fan  200  of a modification. The inline axial flow fan  200  includes a cylindrical housing  250  that accommodates a first fan  10  and a second fan  20  similar to those of the above-described example embodiment. 
     The inline axial flow fan  200  has a disk-shaped flange  30  that extends radially outward from an outer peripheral surface of the first case  12  or the second case  22  at an intermediate position in the axial direction between the first fan  10  and the second fan  20 . That is, the inline axial flow fan  200  is configured such that the housing  250  has a cylindrical shape extending in the axial direction, and the first case  12  and the second case  22  are cylindrical at least in a part from the first slits  12 B to the second slits  22 B in the axial direction. 
     Moreover, the inline axial flow fan  200  has multiple second partition plates  240  that are bridged between an inner peripheral surface of the housing  250  and an outer peripheral surface of the second case  22  in the radial direction. The inline axial flow fan  200  of the example embodiment has four second partition plates  240  that are arranged at 90-degrees intervals in the circumferential direction. The number of second partition plates  240  is not particularly limited. Note that although illustration is omitted, the inline axial flow fan  200  has multiple first partition plates extending radially from an outer peripheral surface of the first case  12  to an inner peripheral surface of the housing  250  outside the lower first case  12 . 
     The four second partition plates  240  shown in  FIG. 5  divide a space surrounded by the housing  250 , the second case  22 , and the flange  30  into four spaces  201 ,  202 ,  203 , and  204  in the circumferential direction. The second partition plate  240  blocks circulation of air in the circumferential direction between the adjacent spaces  201  and  202 . Similarly to the second partition plate  240 , the multiple first partition plates provided on the outer periphery side of the first case  12  also divide a space radially outward of the first case  12  into multiple spaces arranged in the circumferential direction. 
     According to the inline axial flow fan  200  of the modification, the space radially outward of the second case  22  is divided into four spaces  201  to  204  by the multiple second partition plates  240 . As a result, the air discharged to the space  201  outside the second case  22  from the second slits  22 B can be prevented from flowing to the adjacent spaces  202  and  204  through the outside of the second case  22 , for example. 
     Hence, according to the inline axial flow fan  200  of the modification, it is possible to suppress generation of circulating air in the circumferential direction outside the second case  22 , so that reduction in the static pressure characteristics due to circulating air can be suppressed. As a result, according to the inline axial flow fan  200 , both low noise and high static pressure can be achieved. 
     Note that the first partition plate and the second partition plate  240  may be provided in the inline axial flow fan  100  shown in  FIGS. 1 to 4 . For example, a second partition plate  240  extending in the radial direction may be provided in the narrow portion  105  shown in  FIG. 4 . According to this configuration, in the inline axial flow fan  100 , the circulation of air in the circumferential direction through the narrow portion  105  can be further reduced. As a result, the decrease in static pressure is further suppressed, which also contributes to noise reduction. 
     While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.