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| Surge arrestor |
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| Surge suppression system for submersible electrical motors |
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| Submersible pump |
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| Submersible pump support |
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| Submersible motor unit |
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| Submersible motor unit |
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| End shield constructed with a separate component holder |
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| Cover for electric motor |
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Motor
| Details |
Inventors: Iwaki, Tadao; Kawawada, Naoki; Ohta, Atsushi; Nitadori, Koji;
Assignee: Seiko Instruments Inc. (JP)
Primary Examiner: Nguyen; Tran
Assistant Examiner:
Attorney, Agent or Firm: Adams & Wilks
A motor has an armature disposed on one of a rotor and a stator and a permanent magnet disposed on the other of the rotor and the stator. The permanent magnet has skewed magnetic poles being magnetized so that a boundary between each pair of skewed magnetic poles is generally S-shaped and opposed areas of pole surfaces of the permanent magnet and the armature gradually increase when the pole surface of the permanent magnet enters a magnetic field region of the pole surface of the armature or gradually decrease when the pole surface of the permanent magnet leaves a magnetic field region of the pole surface of the armature. |
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DETAILED DESCRIPTION Therefore, it is an object of the present invention to suppress the cogging phenomenon from occurring in a motor, such as a spindle motor.
A motor according to the invention includes a permanent magnet arranged on one of a rotor and a stator, and an armature arranged on the other of the rotor and the stator.
The permanent magnet is magnetized such that opposed areas of pole surfaces of the permanent magnet and the armature gradually increase when the pole surface of the permanent magnet enters a magnetic field region of the pole surface of the armature or gradually decrease when the pole surface of the permanent magnet leaves a magnetic field region of the pole surface of the armature.
As a result of various studies by the present inventors, it was revealed that cogging phenomenon occurs due to rapid change of a magnetic field distribution formed by the permanent magnet and armature when the permanent magnet at its pole surface enters and leaves a magnetic field region of the pole surface of the armature.
Accordingly, when the permanent magnet at its pole surface enters a magnetic field region of the pole surface of the armature, if the pole surface opposed areas of the permanent magnet and armature gradually increase, the change rate of a magnetic field distribution formed by the permanent magnet and armature decreases, resulting in less possibility of causing cogging phenomenon.
Also, when the permanent magnet at its pole surface leaves a magnetic field region of the pole surface of the armature, if the pole surface opposed areas of the permanent magnet and armature gradually decrease, the change rate of a magnetic field distribution formed by the permanent magnet and armature decreases, resulting in less possibility of causing cogging phenomenon.
Therefore, the present invention suppresses cogging phenomenon from occurring.
The permanent magnet may have a cylindrical form having the pole surface in an inner peripheral surface thereof, and the armature can be arranged on an inner side of the permanent magnet
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