Patent Publication Number: US-2023155432-A1

Title: Motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. national stage of application No. PCT/JP2020/034773, filed on Sep. 14, 2020, and with priority under 35 U.S.C. § 119(a) and 35 U.S.C. § 365(b) being claimed from Japanese Patent Application No. 2020-048172, filed on Mar. 18, 2020, the entire disclosures of which are hereby incorporated herein by reference. 
    
    
     1. FIELD OF THE INVENTION 
     The present disclosure relates to a motor. 
     2. BACKGROUND 
     A synchronous multiphase AC motor, which is a conventional rotating electrical machine, includes a motor including a cylindrical rotor and a stator disposed concentrically with the rotor inside the rotor. A motor in which a plurality of permanent magnets are arranged along a circumferential direction of an inner peripheral portion of a rotor has been known. The plurality of permanent magnets are configured using a magnet array called a “Halbach array”. That is, the plurality of permanent magnets include a first magnet whose magnetization direction is a radial direction and a second magnet whose magnetization direction is a circumferential direction, and the first magnet and the second magnet are alternately arranged along the circumferential direction. 
     In the motor described above, since magnetic saturation occurs in the magnet holder, there is a problem that a leakage flux is generated, and the power of the motor is reduced by the amount of the leakage flux. 
     SUMMARY 
     A motor according to an example embodiment of the present disclosure includes a cylindrical rotor core, and a magnet group including first magnets and second magnets alternately arranged along a circumferential direction of the rotor core. A first magnetic flux line generated in the first magnets extends along a radial direction of the rotor core, and a second magnetic flux line generated in the second magnets is inclined with respect to the first magnetic flux line. The rotor core includes an inner portion located on a radially inner side of the magnet group and an outer portion located on a radially outer side of the magnet group. The outer portion includes a first iron core that covers the first magnet from the radially outer side, and a second iron core that covers at least a portion of the second magnet in the central axis direction of the rotor core from the radially outer side. 
     The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic partial cross-sectional view illustrating a motor according to an example embodiment of the present disclosure. 
         FIG.  2    is an enlarged perspective view of the motor illustrated in  FIG.  1   . 
         FIG.  3    is an enlarged perspective view of a rotor provided to the motor illustrated in  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS.  1  to  3   , motors according to example embodiments of the present disclosure will be described. 
     A motor  1  illustrated in  FIG.  1    is, for example, a motor used by being mounted on a vehicle such as an automobile. The motor  1  includes a rotor  11  and a stator  9 . 
     As illustrated in  FIG.  2   , the stator  9  includes a cylindrical core back  91  and a plurality of teeth (protrusions)  92  provided on an inner peripheral portion of the core back  91 . The plurality of teeth  92  protrude radially toward the central axis O 1  of the motor  1 . A coil (not illustrated) having conductivity is wound around each of the teeth  92 . 
     As illustrated in  FIG.  1   , a rotor  11  is disposed concentrically with the stator  9  inside the stator  9 . The rotor  11  is supported so as to be rotatable about the central axis O 1  of the motor  1 . The rotor  11  includes a rotor core  2  and a magnet group  8 . 
     The rotor core  2  has a cylindrical shape as a whole. 
     The magnet group  8  includes first magnets  81  and second magnets  82  alternately arranged at intervals along the circumferential direction of the rotor core  2 . Both the first magnet  81  and the second magnet  82  are formed of permanent magnets, and the same number of permanent magnets are arranged. 
     As illustrated in  FIGS.  2  and  3   , the rotor core  2  includes an inner portion  3  located on a radially inner side (on the central axis O 1  side) of the magnet group  8 , an outer portion  4  located on a radially outer side of the magnet group  8 , and a connecting portion  5  connecting the inner portion  3  and the outer portion  4 . 
     The inner portion  3  has a cylindrical shape. 
     The outer portion  4  is provided along the circumferential direction of the inner portion  3 . The outer portion  4  is disposed radially outside the first magnet  81  and the second magnet  82 . As a result, the eddy current loss is reduced. 
     The connecting portion  5  is provided between the inner portion  3  and the outer portion  4 . As a result, when the rotor core  2  is manufactured, the inner portion  3 , the outer portion  4 , and the connecting portion  5  can be integrally molded using a molding die. As a result, the rotor core  2  can be easily and quickly manufactured. A plurality of the connecting portions  5  are disposed along the circumferential direction of the inner portion  3 . As a result, the inner portion  3  and the outer portion  4  can be stably and firmly connected. 
     The inner portion  3 , the outer portion  4 , and the connecting portion  5  are not limited to being integrally molded. For example, when the rotor core  2  is manufactured, for example, a T-shaped magnetic body in which a second iron core  42  described later and the connecting portion  5  are integrated may be inserted between the second magnets  82 . In this case, it is preferable that the second magnet  82  and the second iron core  42  are fixed with an adhesive or the like. 
     The constituent material of the rotor core  2  is not particularly limited. The rotor core  2  is made of, for example, a magnetic material, and examples of the constituent material (soft magnetic material) of the magnetic material include electromagnetic steel (silicon steel), carbon steel, structural steel, pure iron, soft iron, and stainless permalloy. 
     The magnet group  8  is held between the inner portion  3  and the outer portion  4 . As described above, the magnet group  8  includes a plurality of first magnets  81  and a plurality of second magnets  82  alternately arranged along the circumferential direction of the rotor core  2 . Each of the first magnets  81  and each of the second magnets  82  have an elongated shape along the central axis O 1  direction, that is, a bar shape or a plate shape. 
     As illustrated in  FIGS.  1  and  2   , a first magnetic flux line ML 1  is generated in each of the first magnets  81 . Each of the first magnetic flux lines ML 1  extends along the radial direction of the rotor core  2 . In particular, in the present example embodiment, among the first magnets  81  adjacent to each other in the circumferential direction via the second magnet  82 , the first magnetic flux line ML 1  of one of the first magnets  81  is a first magnetic flux line ML 1 A directed to the inner side of the rotor core  2 , that is, toward the central axis O 1 . The first magnetic flux line ML 1  of the other first magnet  81  is a first magnetic flux line ML 1 B directed to the outer side of the rotor core  2 , that is, in a direction away from the central axis O 1 . 
     In each of the second magnets  82 , a second magnetic flux line ML 2  is generated. Each of the second magnetic flux lines ML 2  is inclined with respect to a virtual line VL (first magnetic flux line ML 1 ) connecting the center of the second magnet  82  and the central axis O 1 . In particular, in the present example embodiment, the second magnet  82  is divided into two small magnets so that the directions of the second magnetic flux lines ML 2  are different. Hereinafter, one of the two small magnets is referred to as a “first divided magnet (first small magnet)  821 ”, and the other small magnet is referred to as a “second divided magnet (second small magnet)  822 ”. A connecting portion  5  is positioned between the first divided magnet  821  and the second divided magnet  822 . 
     The second magnetic flux line ML 2  of the first divided magnet (first small magnet)  821  is the second magnetic flux lines ML 2 A directed toward the inner side of the rotor core  2 . The second magnetic flux line ML 2  of the second divided magnet  822  is the second magnetic flux lines ML 2 B directed toward the outer side of the rotor core  2 . Both the second magnetic flux line ML 2 A and the second magnetic flux line ML 2 B are inclined with respect to the virtual line VL. An inclination angle θ 2 A of the second magnetic flux line ML 2 A with respect to the virtual line VL and an inclination angle θ 2 B of the second magnetic flux line ML 2 B with respect to the virtual line VL are, for example, preferably larger than 0 degrees and equal to or smaller than 90 degrees, and more preferably, equal to or larger than 25 degrees and equal to or smaller than 65 degrees. 
     As illustrated in  FIG.  3   , the outer portion  4  includes a first iron core  41  and a second iron core  42 . 
     The first iron core  41  is disposed facing the first magnet  81 . The first iron core  41  has a plate shape along the central axis O 1  direction, and covers the entire outer surface (front surface)  813  of the first magnet  81  from the radially outer side. 
     The second iron core  42  is disposed facing the second magnet  82 , that is, both the first divided magnet  821  and the second divided magnet  822 . The second iron core  42  has a plate shape along the circumferential direction of the rotor core  2 , and covers at least a part of the outer surface (front surface)  823  of the second magnet  82  in the central axis O 1  direction (central axis of the rotor core  2 ) from the radially outer side. In the present example embodiment, two second iron cores  42  are arranged at a distance from each other in the central axis O 1  direction per second magnet  82 . 
     With the outer portion  4  having such a configuration, the magnetic flux can be attracted to the first iron core  41  and the second iron core  42  made of the material (magnetic body) having a relatively high magnetic permeability. As a result, the leakage flux is reduced (hereinafter referred to as “leakage flux reduction effect”). The power of the motor  1  can be improved by the leakage flux reducing effect and the direction of each magnetic line described above. 
     In particular, in the present example embodiment, as described above, two second iron cores  42  are disposed per one second magnet  82 , and each second iron core  42  partially covers the outer surface  823  of the second magnet  82 . As a result, the leakage flux reduction effect is improved. 
     A thickness t 82  along the radial direction of the second magnet  82  is thicker than a thickness t 81  along the radial direction of the first magnet  81 . As a result, the thickness t 42  of the second iron core  42  can be made thinner than the thickness t 41  of the first iron core  41 , and the rotor core  2  (outer portion  4 ) can be a cylindrical body. As a result, the rotor core  2  can rotate stably. In the second iron core  42  having the smaller thickness t 42 , the magnetic flux remaining in the second iron core  42  can be reduced. 
     Although the motor of the present disclosure has been described above with reference to the illustrated example embodiment, the present disclosure is not limited thereto, and each unit constituting the motor can be replaced with a unit having any configuration capable of exhibiting similar functions. Further, any component may be added. 
     Features of the above-described example embodiments and the modifications thereof may be combined appropriately as long as no conflict arises. 
     While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.