| 摘要 |
The present invention provides a dipole-ring magnetic circuit having a greater magnetic field strength and demagnetization resistance. A dipole-ring magnetic circuit including permanent magnet pieces arranged in an annular shape that magnetization directions make one rotation halfway around the shape, in which the permanent magnet pieces produce a substantially one-directional magnetic field at a uniform strength in an interior space surrounded by the permanent magnet pieces; two or more specified magnet pieces have a magnetization direction of forming an angle of from 150 to 210 degrees with respect to the direction of the magnetic field which is on a plane perpendicular to a central axis of the annular shape, and are called“specified magnet pieces”; and at least in each of the specified magnet pieces, a value of magnetic coercive force increases with decreasing distance to the interior space along a radial direction of the annular shape.
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