Permanent-magnet rotor for an inner rotor type electric rotary machine and magnet-saving type rotor for a synchronous motor

Abstract

A total of three permanent magnets, installed in a rotor core closely to an outer cylindrical surface of the rotor core, are disposed at predetermined angular pitches in the circumferential direction of the rotor core. All of the permanent magnets are magnetized in such a manner that the direction of magnetization is the same when seen in the radial direction. A plurality of magnet-less holes, extending in the axial direction in the vicinity of the outer cylindrical surface of the rotor core, are provided between two adjacent permanent magnets.

What is claimed is:  
     
         1 . A permanent-magnet rotor for an inner rotor type electric rotary machine comprising: 
 a rotor core having an outer cylindrical surface facing to an inner cylindrical surface of a stator; and    a plurality of permanent magnets installed in said rotor core closely to said outer cylindrical surface of said rotor core and disposed at predetermined angular pitches in the circumferential direction of said rotor core,    wherein all of said permanent magnets are magnetized in such a manner that the direction of magnetization is the same when seen in the radial direction.    
     
     
         2 . The permanent-magnet rotor for an inner rotor type electric rotary machine in accordance with  claim 1 , wherein said permanent magnets are made of rare-earth magnet.  
     
     
         3 . The permanent-magnet rotor for an inner rotor type electric rotary machine in accordance with  claim 1 , wherein said rotor core has a plurality of magnet-less holes extending in the axial direction in the vicinity of said outer cylindrical surface of the rotor core so as to interpose between two adjacent permanent magnets.  
     
     
         4 . The permanent-magnet rotor for an inner rotor type electric rotary machine in accordance with  claim 3 , wherein each of said magnet-less holes has an elongated cross-sectional shape with a radial size longer than a circumferential size.  
     
     
         5 . The permanent-magnet rotor for an inner rotor type electric rotary machine in accordance with  claim 3 , wherein said magnet-less holes accommodate a basket-type wiring.  
     
     
         6 . The permanent-magnet rotor for an inner rotor type electric rotary machine in accordance with  claim 3 , wherein said magnet-less holes are arrayed in a predetermined matrix pattern with a plurality of lines and rows extending in the circumferential direction and the radial direction.  
     
     
         7 . A magnet-saving type rotor for a synchronous motor comprising: 
 a rotor core, and    a total of k permanent magnets installed in said rotor core closely to an outer cylindrical surface of said rotor core,    wherein said rotor core comprises: 
 a total of k magnet accommodation holes formed in said rotor core for separately accommodating said permanent magnets, so as to extend in an axial direction of said rotor core and being disposed at equal angular pitches of θn (=360/k degrees);  
 a total of 2k magnet-less holes formed in said rotor core for accommodating no permanent magnets, so as to extend in the axial direction of said rotor core and being positioned at both circumferential ends of said k magnet accommodation holes;  
 first magnetic pole portions having a first polarity and positioned at a radial outer side of said magnet accommodation holes in an outer peripheral region of said rotor core; and  
 second magnetic pole portions having a second polarity and positioned between any two of said magnet-less holes arrayed next to each other along the circumferential direction in the outer peripheral region of said rotor core,  
   wherein a sector angle occupied by each of said magnet-less holes positioned at both circumferential ends of respective magnet accommodation holes is equal to θ0 (=0.5(θn−θ1−θ2))    where θ1 represents a sector angle occupied by each of said first magnetic pole portions, θ2 represents a sector angle occupied by each of said second magnetic pole portions, and θ0 represents a sector angle occupied by each of boundary zones intervening between said first magnetic pole portions and said second magnetic pole portions.    
     
     
         8 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 7 , wherein a ratio (θ0/θn) of the sector angle θ0 to the pitch angle θn is in a range from 0.05 to 0.125.  
     
     
         9 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 7 , wherein a ratio (θ2/θ1) of said sector angle θ2 to said sector angle θ1 is in a range from 0.9 to 1.1.  
     
     
         10 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 7 , wherein said permanent magnets are made of rare-earth magnet.  
     
     
         11 . A magnet-saving type rotor for a synchronous motor comprising: 
 a rotor core, and    a total of k permanent magnets installed in said rotor core closely to an outer cylindrical surface of said rotor core,    wherein said rotor core comprises: 
 a total of k magnet accommodation holes formed in said rotor core for separately accommodating said permanent magnets, so as to extend in an axial direction of said rotor core and being disposed at equal angular pitches of θn (=360/k degrees);  
 a total of 2k magnet-less holes formed in said rotor core for accommodating no permanent magnets, so as to extend in the axial direction of said rotor core and being positioned at both circumferential ends of said k magnet accommodation holes;  
   first magnetic pole portions having a first polarity and positioned at a radial outer side of said magnet accommodation holes in an outer peripheral region of said rotor core; and    second magnetic pole portions having a second polarity and positioned between any two of said magnet-less holes arrayed next to each other along the circumferential direction in the outer peripheral region of said rotor core, wherein a ratio (θ2/θ1) of a sector angle θ2 occupied by each of said second magnetic pole portions to a sector angle θ1 occupied by each of said first magnetic pole portions is in a range from 0.9 to 1.1, and a sector angle θ0 occupied by each of boundary zones intervening between said first magnetic pole portions and said second magnetic pole portions is expressed by 0.5(θn−θ1−θ2).    
     
     
         12 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 11 , wherein said sector angle θ0 is equal to a sector angle occupied by each of said magnet-less holes positioned at both circumferential ends of respective magnet accommodation holes.  
     
     
         13 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 11 , wherein a ratio (θ0/θn) of the sector angle θ0 to the pitch angle θn is in a range from 0.05 to 0.125.  
     
     
         14 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 11 , wherein said permanent magnets are made of rare-earth magnet.  
     
     
         15 . A magnet-saving type rotor for a synchronous motor comprising: 
 a rotor core, and    a total of k permanent magnets installed in said rotor core closely to an outer cylindrical surface of said rotor core,    wherein said rotor core comprises: 
 a total of k magnet accommodation holes formed in said rotor core for separately accommodating said permanent magnets, so as to extend in an axial direction of said rotor core and being disposed at equal angular pitches of θn (=360/k degrees);  
 a total of 2k magnet-less holes formed in said rotor core for accommodating no permanent magnets, so as to extend in the axial direction of said rotor core and being formed continuously at both circumferential ends of each of said k magnet accommodation holes;  
 first magnetic pole portions having a first polarity and positioned at a radial outer side of said magnet accommodation holes in an outer peripheral region of said rotor core;  
 second magnetic pole portions having a second polarity and positioned between any two of said magnet-less holes arrayed next to each other along the circumferential direction in the outer peripheral region of said rotor core; and  
 a pair of bridges provided between an outer cylindrical surface of said rotor core and two of said magnet-less holes positioned continuously at both circumferential ends of each magnet accommodation hole,  
 wherein a ratio of the thickness of each of said bridges to a gap between said rotor core and a stator constituting part of said synchronous motor is in a range from 0.5 to 3.  
   
     
     
         16 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 15 , wherein each of said bridges has a uniform thickness in the circumferential direction and a magnetic flux in each bridge is saturated.  
     
     
         17 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 15 , wherein the cross-sectional shape of each of said magnet-less holes is a right triangular shape with a hypotenuse extending along the outer cylindrical surface of said rotor core.  
     
     
         18 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 15 , wherein a circumferential size of said first magnetic pole portion is larger than a circumferential size of said second magnetic pole portion.  
     
     
         19 . A magnet-saving type rotor for a synchronous motor comprising: 
 a rotor core, and    a total of k permanent magnets installed in said rotor core closely to an outer cylindrical surface of said rotor core,    wherein said rotor core comprises: 
 a total of k magnet accommodation holes formed in said rotor core for separately accommodating said permanent magnets, so as to extend in an axial direction of said rotor core and being disposed at equal angular pitches of θn (=360/k degrees);  
 a total of 2k first magnet-less holes formed in said rotor core for accommodating no permanent magnets, so as to extend in the axial direction of said rotor core and being positioned continuously at both circumferential ends of said k magnet accommodation holes;  
 first magnetic pole portions having a first polarity and positioned at a radial outer side of said magnet accommodation holes in an outer peripheral region of said rotor core;  
 second magnetic pole portions having a second polarity and positioned between any two of said first magnet-less holes arrayed next to each other along the circumferential direction in the outer peripheral region of said rotor core; and  
 a plurality of second magnet-less holes formed in said second magnetic pole portions so as to extend in the axial direction in the vicinity of said outer cylindrical surface of the rotor core.  
   
     
     
         20 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 19 , wherein a sector angle occupied by each of said first magnet-less holes positioned continuously at both circumferential ends of respective magnet accommodation holes is equal to θ0 (=0.5(θn−θ1−θ2)), where θ1 represents a sector angle occupied by each of said first magnetic pole portions, θ2 represents a sector angle occupied by each of said second magnetic pole portions, and θ0 represents a sector angle occupied by each of boundary zones intervening between said first magnetic pole portions and said second magnetic pole portions.  
     
     
         21 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 19 , wherein said permanent magnets are made of rare-earth magnet.  
     
     
         22 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 19 , wherein the ratio (θ2/θ1) of the sector angle θ2 occupied by each of the second magnetic pole portions to the sector angle θ1 occupied by each of the first magnetic pole portions is in the range from 0.9 to 1.1.  
     
     
         23 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 19 , wherein a ratio (θ0/θn) of the sector angle θ0 occupied by each of boundary zones to the pitch angle θn is in the range from 0.05 to 0.125.  
     
     
         24 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 19 , wherein each of said second magnet-less holes has an elongated cross-sectional shape with a radial size longer than a circumferential size.  
     
     
         25 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 19 , wherein said second magnet-less holes accommodate a basket-type wiring.  
     
     
         26 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 19 , wherein said second magnet-less holes are arrayed in a predetermined matrix pattern with a plurality of lines and rows extending in the circumferential direction and the radial direction.  
     
     
         27 . A magnet-saving type rotor for a synchronous motor comprising: 
 a rotor core, and    a total of k permanent magnets installed in said rotor core closely to an outer cylindrical surface of said rotor core,    wherein said rotor core comprises: 
 a total of k magnet accommodation holes formed in said rotor core for separately accommodating said permanent magnets, so as to extend in an axial direction of said rotor core and being disposed at equal angular pitches of θn (=360/k degrees);  
 a total of 2k first magnet-less holes formed in said rotor core for accommodating no permanent magnets, so as to extend in the axial direction of said rotor core and being formed continuously at both circumferential ends of each of said k magnet accommodation holes;  
 first magnetic pole portions having a first polarity and positioned at a radial outer side of said magnet accommodation holes in an outer peripheral region of said rotor core;  
 second magnetic pole portions having a second polarity and positioned between any two of said first magnet-less holes arrayed next to each other along the circumferential direction in the outer peripheral region of said rotor core;  
 a pair of bridges provided between an outer cylindrical surface of said rotor core and two of said first magnet-less holes positioned continuously at both circumferential ends of each magnet accommodation hole; and  
 a plurality of second magnet-less holes formed in said second magnetic pole portions so as to extend in the axial direction in the vicinity of said outer cylindrical surface of the rotor core,  
 wherein a ratio of the thickness of each of said bridges to a gap between said rotor core and a stator constituting part of said synchronous motor is in a range from 0.5 to 3.  
   
     
     
         28 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 27 , wherein said permanent magnets are made of rare-earth magnet.  
     
     
         29 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 27 , wherein each of said second magnet-less holes has an elongated cross-sectional shape with a radial size longer than a circumferential size.  
     
     
         30 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 27 , wherein said second magnet-less holes are arrayed in a predetermined matrix pattern with a plurality of lines and rows extending in the circumferential direction and the radial direction.  
     
     
         31 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 27 , wherein each of said bridges has a uniform thickness in the circumferential direction and a magnetic flux in each bridge is saturated.  
     
     
         32 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 27 , wherein the cross-sectional shape of each of said first magnet-less holes is a right triangular shape with a hypotenuse extending along the outer cylindrical surface of said rotor core.  
     
     
         33 . The magnet-saving type rotor for a synchronous motor in accordance with  claim 27 , wherein a circumferential size of said first magnetic pole portion is larger than a circumferential size of said second magnetic pole portion.