| 摘要 |
PURPOSE:To make the lines of magnetic force uniform over a wide range of area in an air gap by a method wherein an auxiliary magnet is arranged at the end part of a pole piece, and it is magnetized in the direction reverse to the lines of magnetic force of the air gap. CONSTITUTION:A box type yoke is formed with soft iron yokes 11, 12 and 13. Main magnets 21 and 22 and pole pieces 31 and 32 are arranged inside the yokes 11 and 13 respectively. Said main magnets are magnetized in the direction as shown by the arrow M in the diagram, and the pole piece 31 becomes N-pole and the pole piece 32 becomes S-pole. Besides, an auxiliary magnet 41, magnetized in the direction reverse to the direction of the magnetic field in the magnetic gap, is arranged on the end part of the pole pieces 31 and 32. According to this constitution, the deterioration in magnetic field strength can be prevented as the lines of magnetic force is absorbed by the yoke 12 at the end part of the pole pieces even when the intervals of the pole pieces is made wider, and the lines of magnetic force is made uniform in the air gap over a wide range. The auxiliary magnet 12 is opposed to the pole pieces 32 and 33, and the ferrite magnet of the relative magnetic permeability mu of almost 1 is obtained.
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