Patent ID: 7701093

Claim:
A linear motor which includes a stator and a movable element, comprising: an armature disposed on one of the stator and the movable element, the armature including: an iron core having three or more magnetic pole portions arranged along a moving direction of the movable element; and armature windings of three phases wound around the iron core to excite the three or more magnetic pole portions; and a permanent magnet magnetic pole row disposed on the other of the stator and the movable element, the permanent magnet magnetic pole row including: a base made of a magnetic material; and a plurality of permanent magnets disposed at a given interval in a row along the moving direction on the base so that north poles and south poles may alternately be arranged, the plurality of permanent magnets facing the three or more magnetic pole portions with a given gap therebetween; wherein a length W 1 , as measured in the moving direction, of each of two permanent magnets which are respectively disposed at either end of the permanent magnet magnetic pole row is less than a length W, as measured in the moving direction, of the remaining permanent magnets; and the number of slots per pole per phase is ⅜, three-eighths; and when a pitch between centers of two adjacent magnetic pole portions of the plurality of magnetic pole portions constituting the armature is defined as τs, the length W of the permanent magnet is defined as W=τs; and a ratio W 1 /W of the length W 1 to the length W is 0.43<W 1 /W<0.49.