Movable iron core linear actuator

A movable iron core linear actuator of which moving element is made to reciprocate, the linear actuator comprising a magnetic circuit which includes:

• an iron core which constitutes the moving element;
• a stator core which includes a facing portion which faces the iron core;
• a pair of permanent magnets disposed in a facing portion along the reciprocating direction, the pair of permanent magnets having inverted magnetic poles at their surfaces which face the iron core;
• and
• a coil wound around the stator core,
• the magnetic circuit causing, via the magnetic flux produced by energization of the coil, the moving element to reciprocate by weakening the magnetic flux produced in the magnet situated in a necessary direction between the pair of permanent magnets, and strengthening the magnetic flux produced in the other magnet, and when the coil is being energized, spring force of a magnetic spring which varies in accordance with a relative position of the moving element with respect to the stator core being superimposed on electromagnetic driving force produced by the energization of the coil and applied to the moving element by the magnetic flux produced by the permanent magnets,
• wherein a space portion having low magnetic permeability compared with the stator core is formed to constitute a magnetic spring adjustment portion which changes magnetic flux distribution, the space portion being formed in a state in which a part of the facing portion is removed in an area, which is the magnetic flux path, between a part of the facing portion of the stator core and the permanent magnet and, by this magnetic spring adjustment portion, the magnetic spring characteristic which is the relationship between the relative position of the moving element with respect to the stator core and the spring force of the magnetic spring is changed compared with a case in which no space portion is formed.