Counter-rotating axial-flow fan device

Abstract

A counter-rotating axial-flow fan device, which requires low power consumption and has an improved flow rate-static pressure characteristic, is provided at low cost. The counter-rotating axial-flow fan device includes a first axial-flow fan unit with first blades and a second axial-flow fan unit with second blades, which are connected in series. The first axial-flow fan unit includes a three-phase motor for rotating the first blades. The second axial-flow fan unit includes a single-phase motor for rotating the second blades. The first blades and the second blades rotate in a direction opposite to each other. In addition, the three-phase motor is driven by controlling the rotation speed thereof.

What is claimed is: 
     
         1 . A counter-rotating axial-flow fan device comprising:
 a first axial-flow fan unit including a plurality of first blades and a three-phase motor for rotating the first blades in a first direction; and   a second axial-flow fan unit including a plurality of second blades and a single-phase motor for rotating the second blades in a direction opposite to the first direction, the second axial-flow fan unit connected with the first axial-flow fan unit in series.   
     
     
         2 . The counter-rotating axial-flow fan device according to  claim 1 , wherein the three-phase motor is driven by controlling a rotation speed thereof. 
     
     
         3 . The counter-rotating axial-flow fan device according to  claim 2 , wherein the first axial-flow fan unit is arranged at a gas intake side of the counter-rotating axial-flow fan device. 
     
     
         4 . The counter-rotating axial-flow fan device according to  claim 3 , wherein the number of first blades in the first axial-flow fan unit is N and the number of second blades in the second axial-flow fan unit is M, and N is greater than M. 
     
     
         5 . The counter-rotating axial-flow fan device according to  claim 3 , wherein the single-phase motor of the second axial-flow fan unit is driven at a constant frequency and at a constant voltage. 
     
     
         6 . The counter-rotating axial-flow fan device according to  claim 5 , wherein the three-phase motor and the single-phase motor are driven at the same voltage. 
     
     
         7 . The counter-rotating axial-flow fan device according to  claim 4 , wherein the single-phase motor of the second axial-flow fan unit is driven at a constant frequency and at a constant voltage. 
     
     
         8 . The counter-rotating axial-flow fan device according to  claim 7 , wherein the three-phase motor and the single-phase motor are driven at the same voltage.