JP2651734B

An electromagnetic actuator includes a cylindrical rod made of a magnetic substance and having a large number of annular teeth formed on an outer surface thereof at a fixed pitch, and a plurality of annular electromagnets fitted on the cylinder rod. The intervals of the annular electromagnets are set such that the offsets between the annular teeth of the annular electromagnets and the annular teeth of the corresponding cylindrical rod gradually increase. This ensures highly accurate axisymmetric configuration which in turn ensures a completely axisymmetric distribution of the magnetic flux. In consequence, the radial force which acts between the electromagnet and the rod can be reduced, and control over the movement of the rod in the axial direction is thus facilitated.