Patent ID: 7385317

Claim:
A linear motor comprising; a first unit having 2n permanent magnet rods arranged parallel at predetermined intervals (n is a natural number) and a rod support member supporting the 2n permanent magnet rods arranged parallel at predetermined intervals, the 2n permanent magnet rods each comprising a magnetically permeable shaft and a permanent magnet row having a plurality of permanent magnets, the permanent magnets being so magnetized that each has a magnetic pole with one polarity on its entire outer circumferential surface and arranged on the shaft in such a manner that opposite polarities alternately appear in an axial direction of the shaft; and a second unit having unit cores and winding sets, the unit cores each having 2n through-holes through which the 2n permanent magnet rods loosely extend respectively, the winding sets each having 2n excitation windings, the excitation windings each being so formed that a winding conductor is wound in a ring-like shape and has a space surrounded by the winding conductor, through which the corresponding permanent magnet rod loosely extends, the winding sets being arranged in such a manner that the excitation windings each corresponds to each of the permanent magnet rods, the unit cores and the winding sets being alternately arranged in the axial direction; wherein the first unit and the second unit are so constructed that one of the first unit and the second unit functions as a moving member and the other as a stator; wherein the 2n permanent magnet rods are so arranged that a positional difference in an electrical angle between each of the permanent magnet rows in the n permanent magnet rods of the 2n permanent magnet rods and each of the permanent magnet rows of the remaining n permanent magnet rods in the 2n permanent magnet rods is 180°; wherein n of the excitation windings in each winding set through which the n permanent magnet rods extend and n of the excitation windings of each winding set through which the remaining n permanent magnet rods extend are excited with a phase difference of 180° in an electrical angle between them, wherein, among the excitation windings arranged in the axial direction, three consecutive excitation windings are excited with a phase difference of 120° in an electrical angle.