Polarized electromagnet

1. A polarized electromagnet comprising:

a spool around which an exciting coil is wound; a movable plunger penetrating the spool; an interior yoke fixed on an outer side of the spool; an exterior yoke disposed to maintain a predetermined interval on an outer side of the interior yoke; and a permanent magnet disposed between the interior yoke and exterior yoke;

wherein the exterior yoke has a pair of end plate portions opposing two ends of the spool, and a linking plate portion linking the pair of end plate portions; and

the interior yoke has a first opposing plate portion opposing the linking plate portion of the exterior yoke, and second opposing plate portions opposing one end plate portion of the exterior yoke, and the first opposing plate portion and the second opposing plate portion are linked without coming close to the exterior yoke.

2. A polarized electromagnet according to claim 1 , wherein in the interior yoke, the first opposing plate portion and the second opposing plate portions are linked by a pair of upper and lower bent portions bending upper and lower end portions of the first opposing plate portion toward an exciting coil side.

3. A polarized electromagnet according to claim 2 , wherein a size between outer sides of the bent portions is set to be equal to or less than a diameter of the exciting coil.

4. A polarized electromagnet according to claim 1 , wherein the permanent magnet is disposed between the linking plate portion of the exterior yoke and the first opposing plate portion of the interior yoke.

5. A polarized electromagnet according to claim 1 , wherein the interior yoke is arranged such that the second opposing plate portions are inserted and fixed in an insertion and holding portion formed on the spool.

6. A polarized electromagnet according to claim 1 , wherein the spool is formed of a non-magnetic body, and has a cylindrical portion which the plunger is inserted through, and rectangular flange portions sandwiching two ends of the exciting coil formed at two ends of the cylindrical portion,

a flange portion of the rectangular flange portions in which the interior yoke is inserted and held is configured of a coil retainer plate portion that contacts with one end portion of the exciting coil, and a frame-like armature housing portion attached to the coil retainer plate portion in a central portion on each side that houses an armature by opening an end portion linked to one end portion of the plunger, and

a projection for positioning the armature is provided in a position opposing the armature of the armature housing portion.