Permanent magnet type rotary electric machine and electrically driven vehicle using the same

Abstract

A plurality of permanent magnets 6 are embedded in a cylindrical rotor core 8 and arranged in a circumferential direction of the rotor core 8 . A pair of side rings 81 are mounted on the axial ends of the rotor core 8 . The outer diameter of each side ring 81 is set smaller than the outer diameter of the rotor core 8 . With this structure, an eddy current generated in each side ring 81 can be suppressed to thereby prevent abnormal heating and accordingly prevent thermal demagnetization of the permanent magnets 6.

What is claimed is:  
     
         1 . A permanent magnet type rotary electric machine comprising: 
 a stator having a cylindrical stator core and a plurality of stator windings wound on said stator core; and    a rotor having a cylindrical rotor core opposed to an inner circumferential surface of said stator core with a given gap defined therebetween, a plurality of permanent magnets embedded in said rotor core and arranged in a circumferential direction of said rotor core, and a pair of retainer plates mounted on the axial ends of said rotor core;    wherein the outer diameter of each of said retainer plates is set smaller than the outer diameter of said rotor core.    
     
     
         2 . A permanent magnet type rotary electric machine according to  claim 1 , wherein the difference between the outer diameter of said rotor core and the outer diameter of each of said retainer plates is set to ½ or more of the difference between the inner diameter of said stator core and the outer diameter of said rotor core.  
     
     
         3 . A permanent magnet type rotary electric machine comprising: 
 a stator having a cylindrical stator core and a plurality of stator windings wound on said stator core; and    a rotor having a cylindrical rotor core opposed to an inner circumferential surface of said stator core with a given gap defined therebetween, a plurality of permanent magnets embedded in said rotor core and arranged in a circumferential direction of said rotor core, and a pair of retainer plates mounted on the axial ends of said rotor core;    wherein each of said retainer plates is formed of a metal material having a resistivity of 10 μΩcm or higher.    
     
     
         4 . A permanent magnet type rotary electric machine comprising: 
 a stator having a cylindrical stator core and a plurality of stator windings wound on said stator core; and    a rotor having a cylindrical rotor core opposed to an inner circumferential surface of said stator core with a given gap defined therebetween, a plurality of permanent magnets embedded in said rotor core and arranged in a circumferential direction of said rotor core, and a pair of retainer plates mounted on the axial ends of said rotor core;    wherein the outer diameter of each of said retainer plates is set smaller than the outer diameter of said rotor core, and each of said retainer plates is formed of a metal material having a resistivity of 10 μΩcm or higher.    
     
     
         5 . A permanent magnet type rotary electric machine comprising: 
 a stator having a cylindrical stator core and a plurality of stator windings wound on said stator core; and    a rotor having a cylindrical rotor core opposed to an inner circumferential surface of said stator core with a given gap defined therebetween, a plurality of permanent magnets embedded in said rotor core and arranged in a circumferential direction of said rotor core, and a pair of nonmagnetic members mounted on the axial ends of said rotor core;    wherein each of said nonmagnetic members is formed of a nonmetal material.    
     
     
         6 . A permanent magnet type rotary electric machine comprising: 
 a stator having a cylindrical stator core and a plurality of stator windings wound on said stator core; and    a rotor having a cylindrical rotor core opposed to an inner circumferential surface of said stator core with a given gap defined therebetween, a plurality of permanent magnets arranged in a circumferential direction of said rotor core, and a pair of retainer plates mounted on the axial ends of said rotor core;    wherein the outer diameter of each of said retainer plates is set smaller than the outer diameter of said rotor core.    
     
     
         7 . A permanent magnet type rotary electric machine comprising: 
 a stator having a cylindrical stator core and a plurality of stator windings wound on said stator core; and    a rotor having a cylindrical rotor core opposed to an inner circumferential surface of said stator core with a given gap defined therebetween, a plurality of permanent magnets arranged in a circumferential direction of said rotor core, and a pair of retainer plates mounted on the axial ends of said rotor core;    wherein each of said retainer plates is formed of a metal material having a resistivity of 10 μΩcm or higher.    
     
     
         8 . A permanent magnet type rotary electric machine comprising: 
 a stator having a cylindrical stator core and a plurality of stator windings wound on said stator core; and    a rotor having a cylindrical rotor core opposed to an inner circumferential surface of said stator core with a given gap defined therebetween, a plurality of permanent magnets arranged in a circumferential direction of said rotor core, and a pair of nonmagnetic members mounted on the axial ends of said rotor core;    wherein each of said nonmagnetic members is formed of a nonmetal material.    
     
     
         9 . An electrically driven vehicle comprising: 
 a battery for supplying a DC voltage;    an inverter for converting said DC voltage supplied from said battery into an AC voltage; and    a permanent magnet type rotary electric machine for outputting a drive torque for driving said vehicle at said AC voltage;    said permanent magnet type rotary electric machine comprising: 
 a stator having a cylindrical stator core and a plurality of stator windings wound on said stator core; and  
 a rotor having a cylindrical rotor core opposed to an inner circumferential surface of said stator core with a given gap defined therebetween, a plurality of permanent magnets embedded in said rotor core and arranged in a circumferential direction of said rotor core, and a pair of retainer plates mounted on the axial ends of said rotor core;  
 wherein the outer diameter of each of said retainer plates is set smaller than the outer diameter of said rotor core.