| 摘要 |
PURPOSE:To widen the range of the driving force of a linear actuator to be constant, by arranging a sub-magnet having poles in the same direction as that of first magnets, near both the ends of the moving units of the first magnets in the moving direction, so that the sub-magnet may be confronted with the first magnets. CONSTITUTION:A sub-magnet 6 is embedded in a yoke 4 so that a magnetic circuit 3 may be confronted with both the front and rear end sections of main permanent magnets 5. The sub-magnet 6 is placed in the same direction as the magnetized direction of the main permanent magnets 5. By the density distribution of magnetic flux for penetrating coils 7 in the moving direction of the coils 7 at a gap center position on the magnetic circuit 3, the characteristic of the magnetic flux which is increased at both the ends and is suddenly reduced is shown. As a result, when the coils 7 are positioned at both the ends, then the magnetic flux for penetrating the coils 7 is averaged, and a flux- generating force on the coils 7 is not reduced compared with the force on the magnetic circuit without the fitted sub-magnet 6. Accordingly, without changing the lengths of the main permanent magnets 5, a range for obtaining the uniform generating force on the coils can be widened.
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