| 简介 |
PROBLEM TO BE SOLVED : To obtain an electromagnetic driving unit for a compact light quantity regulating apparatus, particularly, whose outside diameter is made small.
SOLUTION : A rotor is formed of a permanent magnet 10 with a hollow cylindrical shape having a central shaft, an inner yoke 11 composed of soft magnetic material is disposed in the hollow of the rotor and an outer yoke 16 is disposed on the outer circumference of the rotor. The rotor is obtained by integrally molding the magnet 10 formed of ferromagnetic material such as rare earth plastic in the hollow cylindrical shape with a rotary shaft member constituting a rotation central shaft by the insert-molding of synthetic resin. The yoke is formed of the soft magnetic material such as iron so that the inner yoke 11 may have bar shaft shape and the outer yoke 16 may have cylindrical shape. The driving unit is provided with a coil for exciting the inner and outer yokes 11 and 16, the inner yoke 11 is provided with a shaft portion having a circular cross section at an end portion positioned in the hollow of the rotor, and the rotor is provided with a bearing recess 18c fit to the shaft portion in the hollow respectively, then the shaft portion of the inner yoke 11 slidably fits in the bearing recess 18c of the rotor. |
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