Patent ID: 7696654

Claim:
A linear motor comprising: a first unit having 3n permanent magnet rods arranged parallel at predetermined intervals (n is a natural number) and a rod support member supporting the 3n permanent magnet rods, the 3n 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 the magnetic poles with 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 3n through-holes through which the 3n permanent magnet rods loosely extend respectively, the winding sets each having 3n excitation windings, the excitation windings each being so formed that a winding conductor 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 3n permanent magnet rods is divided into three groups, and the permanent magnet rows of n permanent magnet rods in a first group, the permanent magnet rows of n permanent magnet rods in a second group, and the permanent magnet rows of n permanent magnet rods in a third group are arranged with a positional difference of 120° in an electrical angle from each other; wherein n of the excitation windings of each winding set through which the n permanent magnet rods in the first group extend, n of the excitation windings of each winding set through which the n permanent magnet rods in the second group extend, and n of the excitation windings of each winding set through which the n permanent magnet rods in the third group extend are excited with a phase difference of 120° in an electrical angle form each other.