JPS6419959A - Polyphase linear stepper motor - Google Patents

Abstract

PURPOSE:To prevent the inhibition of the movement of a moving piece, and to scale down an air gap by simultaneously generating attraction and repulsion forces where opposite at 180 deg. mutually and dispersing attraction and repulsion forces to the outer circumferential section of the moving piece. CONSTITUTION:A stator 11 consists of a stator yoke 8 and four stator poles 9A-9D projecting to the inside in the radial direction, and a moving piece 12 is arranged inside the stator 11 through an air gap. In the stator 11, the radii r1 of the inner circumferential surfaces of the stator poles 9A, 9B are made to differ from those of the inner circumferential surfaces of 9C and 9D (r2>r1), and the stator poles are all laminated in the axial direction in succession while being mutually displaced at 180 deg. as sheets (t) thick. The moving piece 12 is formed by a magnetic substance disk 13a, which is (t) thick and the radius of an outer circumferential surface of which takes a value r3 slightly smaller than r1, a disk 13b, which is (t) thick and the radius of an outer circumferential surface of which is made smaller than the disk 13a by (t), and a discoid permanent magnet 2t thick, mutually opposite two sections in the outer circumference of the disk 13a are formed to a shape that the two sections are displaced at every approximately t/2 from the outer circumferential surface extending over 90 deg. in the circumferential direction, and these disks are laminated successively, thus constituting the moving piece 12.