Composite magnet structure for rotor

Abstract

An interior permanent magnet electric motor. A rotor comprising a slot radially spaced from its longitudinal axis of rotation extending parallel to the axis. First and second magnets are positioned in the slot and extend parallel to the axis. A first magnet is positioned between a second magnet and the axis.

1 . An electric motor rotor comprising: 
 a core having a central longitudinal axis and a slot radially spaced from the longitudinal axis and extending parallel to the axis; and    first and second magnets positioned in the slot and extending parallel to the longitudinal axis, wherein the first magnet is positioned between the second magnet and the longitudinal axis.    
   
   
       2 . The rotor of  claim 1  wherein said core has an outer surface parallel to said longitudinal axis, said outer surface having a lobe.  
   
   
       3 . The rotor of  claim 2  further comprising an air space adjacent to the first or second magnet.  
   
   
       4 . The rotor of  claim 1  wherein, when viewed in cross section, the first magnet is arch-shaped, having a convex surface facing the central longitudinal axis and a concave surface facing the second magnet.  
   
   
       5 . The rotor of  claim 4  wherein at least one of the following: 
 (1) when viewed in cross section, the second magnet has a convex surface generally complementary to and in contact with the concave surface of the first magnet; and    (2) when viewed in cross section, at least a portion of the first magnet contacts the concave surface of the second magnet.    
   
   
       6 . The rotor of  claim 1  further comprising a third magnet of the same material as the second magnet sized and shaped substantially the same as the second magnet.  
   
   
       7 . The rotor of  claim 6  wherein, when viewed in cross section, the second and third magnets are substantially rectangular and at least a portion of each is in contact with the first magnet.  
   
   
       8 . The rotor of  claim 1  wherein one of the first or second magnets is strontium ferrite, the other of the first and second magnets is neodymium-iron-boron, and the core is steel.  
   
   
       9 . A method of producing an electric motor comprising: 
 forming a slot in a rotor core having a central longitudinal axis;    inserting a first magnet in the slot;    inserting a second magnet in the slot, wherein said first magnet is substantially between the second magnet and the central longitudinal axis;    inserting the rotor core into a stator having windings; and    connecting the windings of the stator to a commutation circuit.    
   
   
       10 . The method of  claim 9  wherein the first magnet is strontium ferrite, the second magnet is neodymium-iron-boron, and the core is steel.  
   
   
       11 . An electric motor comprising: 
 a rotor including: 
 a core having a central longitudinal axis and a slot radially spaced from the longitudinal axis and extending parallel to the axis; and  
 first and second magnets positioned in the slot and extending parallel to the longitudinal axis, wherein the first magnet is positioned between the second magnet and the longitudinal axis;  
 a stator in magnetic coupling relation to the rotor having windings; and  
 a commutation circuit electrically connected to the windings of the stator.  
   
   
   
       12 . The rotor of  claim 11  wherein said core has an outer surface parallel to said longitudinal axis, said outer surface having a lobe.  
   
   
       13 . The motor of  claim 12  further comprising an air space adjacent to the first or second magnet.  
   
   
       14 . The motor of  claim 11  wherein, when viewed in cross section, the first magnet is arch-shaped, having a convex surface facing the central longitudinal axis and a concave surface facing the second magnet.  
   
   
       15 . The motor of  claim 14  wherein at least one of the following: 
 (1) when viewed in cross section, the second magnet has a convex surface generally complementary to and in contact with the concave surface of the first magnet; and    (2) when viewed in cross section, at least a portion of the first magnet contacts the concave surface of the second magnet.    
   
   
       16 . The motor of  claim 11  further comprising a third magnet of the same material as the second magnet sized and shaped substantially the same as the second magnet.  
   
   
       17 . The motor of  claim 16  wherein, when viewed in cross section, the second and third magnets are substantially rectangular and at least a portion of each is in contact with the first magnet.  
   
   
       18 . The motor of  claim 17  wherein, when viewed in cross section, the second and third magnets are spaced apart.  
   
   
       19 . The motor of  claim 11  wherein the rotor has at least two slots equally spaced radially and circumferentially about the longitudinal axis.  
   
   
       20 . The motor of  claim 11  wherein one of the first or second magnets is strontium ferrite, the other of the first and second magnets is neodymium-iron-boron, and the core is steel.