Serial axial fan unit

Abstract

A serial axial fan unit includes first and second axial fans and a spacer arranged therebetween and connected thereto. First and second impellers respectively provided in the first and second axial fans have a diameter in a range from approximately 25 mm to approximately 200 mm, for example. The axial height of the spacer is in a ranged of approximately 1.5 mm to approximately 8 mm, for example. Due to the spacer, the first and second axial fans are spaced apart from each other by an appropriate distance. Thus, a harsh noise caused by interference occurring when air from the first axial fan flows into the second axial fan is reduced. Also, the static pressure to airflow volume characteristics of the serial axial fan for a given sound value is improved.

1 . A serial axial fan unit comprising:
 a first axial fan and a second axial fan coaxial with each other and arranged in an axial direction substantially parallel to a center axis thereof; and   a spacer arranged between the first axial fan and the second axial fan; wherein   each of the first axial fan and the second axial fan includes:
 an impeller having a plurality of blades which are arranged around the center axis so as to extend away from the center axis; 
 a motor portion arranged to rotate the impeller; 
 a housing surrounding the impeller from outside in a radial direction substantially perpendicular to the center axis; 
   the spacer includes a wall portion connected to the housing of each of the first axial fan and the second axial fan, the wall portion defining a space therein in which air flows;   a radius of the impeller of each of the first axial fan and the second axial fan is in a range of approximately 12.5 mm to approximately 100 mm; and   an axial height of the spacer is in a range from approximately 1.5 mm to approximately 8 mm.   
   
   
       2 . The serial axial fan unit according to  claim 1 , wherein the axial height of the spacer is in a range from approximately 5 mm to approximately 7 mm. 
   
   
       3 . The serial axial fan unit according to  claim 1 , wherein
 an inner side surface of the wall portion of the spacer includes a first spacer edge adjacent to the first axial fan and a second spacer edge adjacent to the second axial fan;   an inner side surface of the housing of the first axial fan includes a first housing edge adjacent to the spacer, and an inner side surface of the housing of the second axial fan includes a second housing edge adjacent to the spacer; and   the first spacer edge is substantially aligned with or radially outward of the first housing edge, and the second spacer edge is substantially aligned with or radially outward of the second housing edge.   
   
   
       4 . The serial axial fan unit according to  claim 3 , wherein the first spacer edge is substantially aligned with the first housing edge, and the second spacer edge is substantially aligned with the second housing edge. 
   
   
       5 . The serial axial fan unit according to  claim 1 , wherein each of the first axial fan and the second axial fan further includes a plurality of supporting ribs arranged around the center axis, the supporting ribs extending outward from the corresponding motor portion in the radial direction and being connected to the corresponding housing, and the impeller and the supporting ribs of the first axial fan and the supporting ribs and the impeller of the second axial fan are arranged in the axial direction in that order. 
   
   
       6 . The serial axial fan unit according to  claim 5 , wherein
 the spacer includes a central portion and a plurality of spacer ribs arranged around the center axis;   the central portion is arranged between the motor portion of the first axial fan and the motor portion of the second axial fan; and   the spacer ribs extend outward from the central portion in the radial direction and are connected to the wall portion, and each of the spacer ribs is arranged between a corresponding one of the supporting ribs of the first axial fan and a corresponding one of the supporting ribs of the second axial fan over substantially its entire length.   
   
   
       7 . The serial axial fan unit according to  claim 1 , wherein
 each of the first axial fan and the second axial fan further includes a plurality of supporting ribs arranged around the center axis, the supporting ribs extending outward from the corresponding motor portion in the radial direction and being connected to the corresponding housing; and   the impeller and the supporting ribs of the first axial fan and the impeller and the supporting ribs of the second axial fan are arranged in the axial direction in that order.   
   
   
       8 . The serial axial fan unit according to  claim 7 , wherein
 the spacer includes a central portion and a plurality of spacer ribs arranged around the center axis;   the central portion is arranged between the motor portion of the first axial fan and the motor portion of the second axial fan; and   the spacer ribs extend outward from the central portion in the radial direction and are connected to the wall portion, and each of the spacer ribs is arranged between a corresponding one of the supporting ribs of the first axial fan and a corresponding one of the supporting ribs of the second axial fan over its entire length.   
   
   
       9 . The serial axial fan unit according to  claim 1 , wherein the impeller of the first axial fan and the impeller of the second axial fan are rotated in opposite directions relative to each other. 
   
   
       10 . The serial axial fan unit according to  claim 1 , wherein the spacer is made of a material that absorbs or reduces vibration transferred between the first axial fan and the second axial fan. 
   
   
       11 . The serial axial fan unit according to  claim 1 , wherein
 the housing of each of the first axial fan and the second axial fan is provided with a housing engagement portion at a portion thereof adjacent to the spacer;   the wall portion is provided with a first spacer engagement portion at a portion thereof adjacent to the first axial fan and a second spacer engagement portion at a portion thereof adjacent to the second axial fan; and   the first spacer engagement portion and the second spacer engagement portion engage with the housing engagement portion of the first axial fan and the housing engagement portion of the second axial fan, respectively, to connect the housing of the first axial fan and the housing of the second axial fan to the spacer in a detachable manner.   
   
   
       12 . The serial axial fan unit according to  claim 11 , wherein the housing engagement portion of the first axial fan and the second spacer engagement portion have substantially the same shape as each other, and the first spacer engagement portion and the housing engagement portion of the second axial fan have substantially the same shape as each other. 
   
   
       13 . The serial axial fan unit according to  claim 1 , wherein
 both axial end portions of the housing have an approximately square outer shape;   the spacer has an approximately square outer shape which is substantially aligned with the outer shape of the end portions of the housing of each of the first axial fan and the second axial fan;   the spacer is provided with a spacer guiding portion guiding a lead wire group from the second axial fan to the first axial fan, the spacer guiding portion being arranged between an inner side surface and the outer shape of the spacer; and   the housing of the first axial fan is provided with a housing guiding portion guiding the lead wire group substantially parallel to the center axis to outside of the first axial fan, the housing guiding portion being arranged between an inner side surface and the outer shape of the housing of the first axial fan.