Permanent magnet for motor, motor and magnetizing method

Abstract

The present invention relates to a cylindrical permanent magnet which is used in a micro DC brushless motor used in a compact hard disc etc. An Sm—Co based magnetic material is used as a magnetic material and the permanent magnet has domains magnetized in a radial direction and arranged at regular intervals in a circumferential direction. Provided that P represents a pitch corresponding to an average of an inner circumferential length and outer circumferential length in one of the domains, D denotes an inner diameter of the permanent magnet, t represents a thickness in the radial direction, N represents the number of domains, and M represents the number of AC phases for driving the motor, D is set to 20 (mm) or smaller and t is set to satisfy the relation of t≦πD / (NM−π).

Description

TECHNICAL FIELD [0001] The present invention relates to a motor, for example, a motor including a rotor provided with a permanent magnet. BACKGROUND ART [0002] In recent years, computers have been put in widespread use in a rapid pace. Disc-like storage media such as a hard disc and a magneto-optic disc are widely used for storage devices in most of those computers. Those storage media are rotated at a high speed by a small-sized motor provided to a disc drive and data is read or written from and to the media. [0003] The motor used for the disc drive is designed to generate a rotating magnetic field by means of a stator coil so as to act on a permanent magnet provided to a rotor, thereby rotating. [0004] The permanent magnet is magnetized radially (in a radial direction) and inverts polarities at a predetermined pitch along a circumferential direction. That is, the N pole and the S pole appear at regular intervals along an inner or outer circumference. The same polarity is attained ...

AI Technical Summary

Benefits of technology

[0021] The present invention provides, in order to attain the above-mentioned object, a permanent magnet for a motor, which is disposed in a rotor for the motor and has a cylindrical shape, including domains that are magnetized in a radial direction and are arranged at regular intervals in a circumferential direction, ch

Problems solved by technology

As a result, there is a problem that full magnetization (magnetic saturation) for the permanent magnet is not always allowed and the ability inherent in the magnetic material cannot be completely brought out.

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