Radial anisotropic sintered magnet and its production method, magnet rotor using sintered magnet, and motor using magnet rotor

A method of producing a radial anisotropic sintered magnet, comprising the steps of:

• preparing a metal mold having a core including, in at least part thereof, a ferromagnetic body having a saturated magnetic flux density of 5 kG or more;
• packing a magnet powder in a cavity of the metal mold;
• and
• molding the magnet powder while applying an orientation magnetic field to the magnet powder by a horizontal-field vertical molding process.

A method of producing a radial anisotropic sintered magnet, comprising the steps of:

• preparing a metal mold having at least one non-magnetic body in a die portion of the metal mold so as to be located in a region spread radially from the center of the metal mold at a total angle of 20° or more and 180° or less;
• packing a magnet power in a cavity of the metal mold;
• and
• molding the magnet power while applying a magnetic field to the magnet power by a vertical-field vertical molding process.

A method of producing a radial anisotropic magnet, comprising the steps of:

• preparing a metal mold having a core including, in at least part thereof, a ferromagnetic body having a saturated magnetic flux density of 5 kG or more;
• packing a magnet powder in a cavity of the metal mold;
• and
• molding the magnet powder while applying an orientation magnetic field to the magnet powder by a horizontal-field vertical molding process;
• wherein said method further comprises at least one of the following steps (i) to (v):
• (i) rotating, during the period in which the magnetic field is applied to the magnet powder, the magnet powder in the peripheral direction of the metal mold at a specific angle;
• (ii) rotating, after the magnetic field is applied to the magnet powder, the magnet powder in the peripheral direction of the metal mold at a specific angle, and then applying a magnetic field again to the magnet powder;
• (iii) rotating, during the period in which the magnetic field is applied to the magnet powder, a magnetic field generating coil relative to the magnet powder in the peripheral direction of the metal mold at a specific angle;
• (iv) rotating, after the magnetic field is applied to the magnet powder, a magnetic field generating coil relative to the magnet powder in the peripheral direction of the metal mold at a specific angle, and then applying a magnetic field again to the magnet powder;
• and
• (v) disposing two pairs or more of magnetic field generating coils, and applying a magnetic field to the magnet powder by one pair of the magnetic field generating coils, and then applying a magnetic field to the magnet powder by another pair of the magnetic field generating coils.

A permanent magnet motor using a permanent magnet which is multipolar magnetized in the peripheral direction, comprising:

• a stator having a plurality of teeth;
• and
• a radial anisotropic cylindrical magnet assembled in said motor so as to be combined with said stator;
• wherein said radial anisotropic cylindrical magnet is produced by preparing a metal mold having a core including, in at least part thereof, a ferromagnetic body having a saturated magnetic flux density of 5 kG or more, packing a magnet powder in a cavity of the metal mold, and molding the magnet powder while applying an orientation magnetic field to the magnet powder by a horizontal-field vertical molding process;
• and
• assuming that the number of magnetized poles in the peripheral direction of said cylindrical magnet is 2n (n:
• positive integer in a range of 2 or more and 50 or less), the number of said teeth of said stator to be combined with said cylindrical magnet is set to 3 m (m:
• positive integer in a range of 2 or more and 33 or less) and the values 2n and 3m satisfy a relationship of 2n≠3m.