Contra-rotating axial flow fan unit

Abstract

An axial flow fan unit includes an intake side axial flow fan, an exhaust side axial flow fan, and at least one intermediate axial flow fan. Each of the axial flow fans includes an impeller having blades rotatable about a central rotation axis, a motor arranged to rotate the intake side impeller, and a housing having an inner circumferential surface that surrounds the impeller. The rotational direction of the impeller in the intermediate axial flow fan is different from that of the impellers adjacent thereto.

1 . An axial flow fan unit comprising:
 an intake side axial flow fan including:
 an intake side impeller arranged to rotate about a central rotation axis and having intake side blades; 
 an intake side motor arranged to rotate the intake side impeller; and 
 an intake side housing having an inner circumferential surface that surrounds the intake side impeller; 
   an exhaust side axial flow fan including:
 an exhaust side impeller arranged to rotate about the central rotation axis and having exhaust side blades; 
 an exhaust side motor arranged to rotate the exhaust side impeller; and 
 an exhaust side housing having an inner circumferential surface that surrounds the exhaust side impeller; and 
   at least one intermediate axial flow fan arranged between the intake side axial flow fan and the exhaust side axial flow fan, each of the at least one intermediate axial flow fan including:
 an intermediate impeller arranged to rotate about the central rotation axis and having intermediate blades; 
 an intermediate motor arranged to rotate the intermediate impeller; and 
 an intermediate housing having an inner circumferential surface that surrounds the intermediate impeller; 
   wherein a rotational direction of the intermediate impeller is different from that of the impellers adjacent thereto.   
   
   
       2 . The axial flow fan unit of  claim 1 , wherein the intake side axial flow fan includes intake side support ribs arranged to interconnect the intake side motor and the intake side housing;
 the exhaust side axial flow fan includes exhaust side support ribs arranged to interconnect the exhaust side motor and the exhaust side housing; and   the intermediate axial flow fan includes intermediate support ribs arranged to interconnect the intermediate motor and the intermediate housing.   
   
   
       3 . The axial flow fan unit of  claim 2 , wherein the intake side support ribs are arranged between the intake side impeller and the intermediate impeller, and the intermediate support ribs are arranged between the intermediate impeller and the exhaust side impeller. 
   
   
       4 . The axial flow fan unit of  claim 3 , wherein the number of the blades in each axial flow fan is different from the number of each of the support ribs axially adjacent to the blades. 
   
   
       5 . The axial flow fan unit of  claim 1 , wherein the intermediate housing is successively arranged with the intake side housing and the exhaust side housing in an axial direction. 
   
   
       6 . The axial flow fan unit of  claim 5 , wherein the intermediate housing is successively arranged with the intake side housing and the exhaust side housing in the axial direction with gaps arranged between each of the housings in the axial direction. 
   
   
       7 . The axial flow fan unit of  claim 2 , wherein the intake side support ribs, the exhaust side support ribs, and the intermediate support ribs are substantially flat. 
   
   
       8 . The axial flow fan unit of  claim 2 , wherein each of the intake side support ribs, the exhaust side support ribs, and the intermediate support ribs has an upper edge and a lower edge. 
   
   
       9 . The axial flow fan unit of  claim 8 , wherein each of the intake side support ribs, the exhaust side support ribs, and the intermediate support ribs has an air receiving surface arranged axially between the upper edge and the lower edge to confront an air stream flowing from the intake side impeller toward the exhaust side impeller. 
   
   
       10 . The axial flow fan unit of  claim 9 , wherein the air receiving surface axially faces an exhaust side of the respective axial fan. 
   
   
       11 . The axial flow fan unit of  claim 2 , wherein each of the intake side support ribs, the exhaust side support ribs, and the intermediate support ribs is inclined with respect to the central rotation axis. 
   
   
       12 . The axial flow fan unit of  claim 11 , wherein each of the intake side blades, the exhaust side blades, and the intermediate blades is inclined with respect to the central rotation axis, the inclination of each of the blades being substantially the same as the inclination of each of the support ribs axially positioned at an intake side of the blades. 
   
   
       13 . The axial flow fan unit of  claim 8 , wherein the upper edge of each of the intake side support ribs is positioned upstream of the lower edge thereof with reference to a rotational direction of the intake side impeller;
 the upper edge of each of the exhaust side support ribs is positioned upstream of the lower edge thereof with reference to a rotational direction of the exhaust side impeller; and   the upper edge of each of the intermediate support ribs is positioned upstream of the lower edge thereof with reference to a rotational direction of the intermediate impeller.   
   
   
       14 . The axial flow fan unit of  claim 2 , wherein the intake side support ribs are arranged at an intake side of the intake side housing;
 the intermediate support ribs are arranged between the intake side impeller and the intermediate impeller; and   the exhaust side support ribs are arranged between the intermediate impeller and the exhaust side impeller.   
   
   
       15 . The axial flow fan unit of  claim 1 , wherein the at least one intermediate axial flow fan includes at least a first intermediate axial flow fan and a second intermediate axial flow fan. 
   
   
       16 . The axial flow fan unit of  claim 15 , wherein the intake side axial flow fan includes intake side support ribs arranged to interconnect the intake side motor and the intake side housing;
 the exhaust side axial flow fan includes exhaust side support ribs arranged to interconnect the exhaust side motor and the exhaust side housing; and   each of the intermediate axial flow fans includes intermediate support ribs arranged to interconnect the intermediate motor and the intermediate housing.   
   
   
       17 . The axial flow fan unit of  claim 16 , wherein the intake side support ribs are arranged between the intake side impeller and the intermediate impeller;
 the intermediate support ribs in the first intermediate axial flow fan are arranged between the intermediate impeller in the first intermediate axial flow fan and the intermediate support ribs in the second intermediate axial flow fan; and   the exhaust side support ribs are opposite to the exhaust side impeller away from the intermediate impeller in the second intermediate axial flow fan.   
   
   
       18 . The axial flow fan unit of  claim 17 , wherein the number of the blades in each axial flow fan is different from the number of each of the support ribs axially adjacent to the blades. 
   
   
       19 . The axial flow fan unit of  claim 15 , wherein the intermediate housing of the first intermediate axial flow fan is axially opposite to the intake side housing, the exhaust side housing, or the second intermediate housing. 
   
   
       20 . The axial flow fan unit of  claim 15 , wherein the intermediate housing of the first intermediate axial flow fan is opposite to the intake side housing, the exhaust side housing, or the second intermediate housing with gaps arranged between each of the housings in the axial direction. 
   
   
       21 . The axial flow fan unit of  claim 16 , wherein the intake side support ribs are arranged at an intake side of the intake side housing;
 the intermediate support ribs in the first intermediate axial flow fan are arranged between the intake side impeller and the intermediate impeller in the first intermediate axial flow fan, or between the intermediate impeller in the first intermediate axial flow fan and the intermediate impeller in the second intermediate axial flow fan; and   the exhaust side support ribs are arranged between the exhaust side impeller and the intermediate impeller in the second intermediate axial flow fan.