Electric axial flow pump

Abstract

An electric axial flow pump comprising: a stator 6 having a field coil 10, a rotor 3 including a cylindrical hollow shaft 4 having open ends surrounded by the stator and a plurality of magnets 5 fixed around the hollow shaft, and a flow generation section 2 fixed inside the hollow shaft for rotating integrally with the rotor when the field coil is excited, thereby generating flow of a fluid 15 inside the hollow shaft.

1 . An electric axial flow pump comprising: 
 a stator having a field coil,    a rotor including a cylindrical hollow shaft having open ends surrounded by the stator and a plurality of magnets fixed around the hollow shaft, and    a flow generation section fixed inside the hollow shaft for rotating integrally with the rotor when the field coil is excited, thereby generating flow of a fluid inside the hollow shaft.    
   
   
       2 . The electric axial flow pump according to  claim 1 , wherein the stator is a claw pole type stator.  
   
   
       3 . The electric axial flow pump according to  claim 2 , wherein the stator has a plurality of claw poles formed by compacting insulating-coated magnetic powder on the inner peripheral surface and a circular ring-shaped stator magnetic core for covering the field coil, and the field coil is a circular coil mounted inside the stator magnetic core.  
   
   
       4 . The electric axial flow pump according to  claim 1 , wherein the flow generation section has a fin for rotating integrally with the rotor and moving the fluid in a direction of a rotary shaft of the rotor.  
   
   
       5 . The electric axial flow pump according to claim  4 , wherein the fin is fixed directly to the rotor.  
   
   
       6 . The electric axial flow pump according to  claim 4 , wherein the flow generation section has a pillar installed on the rotary shaft for slowly increasing thickness in the direction of the rotary shaft, and the fin is arranged around the pillar.  
   
   
       7 . The electric axial flow pump according to  claim 1 , wherein the flow generation section has a propeller for rotating integrally with the rotor and moving the fluid in a direction of a rotary shaft of the rotor.  
   
   
       8 . The electric axial flow pump according to  claim 1 , wherein the flow generation section has slits formed inside the hollow shaft in a twisted direction to the direction of the rotary shaft of the rotor.  
   
   
       9 . The electric axial flow pump according to  claim 1 , further comprising: 
 a cylindrical stator frame arranged on an outer periphery of the stator for fixing the stator and    a pair of bearings in a circular ring shape installed inside the stator frame before and behind the rotor for supporting rotatably the rotor, wherein inside diameters of the bearings are larger than an inside diameter of the hollow shaft.    
   
   
       10 . The electric axial flow pump according to  claim 9 , wherein openings at both ends of the stator frame and the openings at the both ends of the hollow shaft are arranged on one straight line and a flow-in direction of the fluid and a flow-out direction thereof are the same direction.  
   
   
       11 . The electric axial flow pump according to  claim 1 , wherein a plurality of the stators are installed in a direction of a rotary shaft of the rotor and to the respective field coils of a plurality of the stators, polyphase AC voltages different in phase are impressed.  
   
   
       12 . The electric axial flow pump according to  claim 1 , wherein so as to permit respective different phases of a three-phase AC power source to be connected one by one to the field coils of the respective stators, the stators are shifted 120° by 120° at an electrical angle and three the stators are arranged in a direction of a rotary shaft of the rotor.  
   
   
       13 . The electric axial flow pump according to  claim 12 , wherein two or more groups of the three stators are installed in the direction of the rotary shaft.  
   
   
       14 . The electric axial flow pump according to  claim 1 , further comprising: 
 a phase splitting section for generating a second single-phase alternating current obtained by shifting a phase of a first single-phase alternating current of a single-phase AC source by 90°, wherein:    so as to permit the first single-phase alternating current and the second single-phase alternating current to be connected one by one to the field coils of the respective stators, the stators are shifted by 90° at an electrical angle and two the stators are arranged in a direction of a rotary shaft.    
   
   
       15 . The electric axial flow pump according to  claim 14 , wherein two or more groups of the two stators are installed in the direction of the rotary shaft.  
   
   
       16 . The electric axial flow pump according to  claim 1 , wherein the rotor has a powder core installed between the hollow shaft and the magnets.  
   
   
       17 . The electric axial flow pump according to  claim 3 , wherein: 
 a thickness of the claw poles in a radial direction is 2 mm or more,    the claw poles have a flat surface perpendicular to a direction of a rotary shaft at an extending end of the rotor in the direction of the rotary shaft and a draft taper inclined at an angle within a range from 8° to 10° to the direction of the rotary shaft tapering from a base of the claw poles to the extending end, and    a ratio of a length of the claw poles in the direction of the rotary shaft to a minimum thickness of the stator magnetic core in the direction of the rotary shaft is less than 5.    
   
   
       18 . The electric axial flow pump according to  claim 17 , wherein assuming the relationship between a number M of the claw poles and an inside diameter D of the stator as M=a·D, a coefficient a is between 0.35 and 0.5.  
   
   
       19 . The electric axial flow pump according to  claim 17  or  18 , wherein a ratio of T/P of an average width angle T of a maximum width angle and a minimum width angle occupied by the claw poles in a peripheral direction of the stator magnetic core to a pitch angle P occupied by a pitch of the claw pole cores in the peripheral direction is between 0.4 and 0.45.  
   
   
       20 . The electric axial flow pump according to  claim 3 , wherein density of the stator magnetic core is 7.5 g/cm 3  or more.