Manufacturing method and magnetizing device for interior permanent magnet rotor unit

1. A method for manufacturing an interior permanent magnet rotor unit that includes a core having a plurality of insertion holes arranged in a circumferential direction of the core and permanent magnets embedded in the insertion holes of the core, the rotor unit or a plurality of the rotor units being coupled in an axial direction of the core to form a rotor, the method comprising:

magnetizing a magnet material filling the insertion holes by using a magnetizing device; wherein

the magnetizing device includes an axial magnetizing part serving as a source of a magnetic field and a radial magnetizing part having an inner peripheral surface that faces the core in a radial direction of the core;

the radial magnetizing part is formed by alternately arranging low magnetic permeability portions and high magnetic permeability portions having higher magnetic permeability than the low magnetic permeability portions in a circumferential direction of the radial magnetizing part; and

in the magnetizing, the radial magnetizing part is disposed so that the low magnetic permeability portions face the magnet materials in the radial direction of the core, the axial magnetizing part is disposed so as to face the radial magnetizing part in the axial direction of the core, and the axial magnetizing part applies the magnetic field toward the radial magnetizing part to apply the magnetic field to the magnet materials via the radial magnetizing part.

2. The method according to claim 1 , wherein

the axial magnetizing part has a circular cylindrical shape, an inner peripheral surface of the axial magnetizing part having a diameter equal to or larger than a diameter of the core; and

in the magnetizing, the inner peripheral surface of the axial magnetizing part is disposed so as to coincide with an outer peripheral surface of the core or so as to be located outside the outer peripheral surface of the core in the radial direction of the core.

3. The method according to claim 2 further comprising:

filling the insertion holes with the magnet materials; wherein

the magnetizing includes at least part of a period of the filling.

4. The method according to claim 3 , wherein

in the filling, a forming guide having guide holes is disposed so as to face an end face of the core in the axial direction of the core, and the guide holes and the insertion holes are filled with the magnet materials;

the method includes compressing the magnet materials by inserting punches into the guide holes to apply pressure to the magnet materials in a direction from the guide holes toward the insertion holes;

in the compressing, the guide holes each have a shape identical to the shape of the insertion holes in section perpendicular to the axial direction of the core, and extend in the axial direction of the core to be connected to the insertion holes; and

the magnetizing includes a period from a start of the compressing to an end of the compressing.

5. The method according to claim 4 , wherein

in the filling, the radial magnetizing part has a length larger than a length of the core in the axial direction of the core, and a portion of the forming guide filled with the magnet materials at the start of the compressing and the core are disposed so as to face the radial magnetizing part in the radial direction of the core.

6. The method according to claim 3 , wherin

the axial magnetizing part is disposed on each side of the core in the axial direction.

7. The method according to claim 3 , wherein

the radial magnetizing part is a circular cylindrical member, and includes a restraining ring;

the restraining ring forms an outer peripheral surface of the radial magnetizing part; and

each of the low magnetic permeability portions and the high magnetic permeability portions extends from the inner peripheral surface of the radial magnetizing part to an inner peripheral surface of the restraining ring.

8. The method according to claim 7 , wherein

the restraining ring is made of a nonmagnetic material.

9. The magnetizing device for use in the method according to claim 1 .