GB1161613A - Pulse-Responsive Stepping Motor - Google Patents

Abstract

1,161,613. Electric motors. W. KOHLHAGEN. 5 Sept., 1966, No. 39603/66. Heading H2A. A stepping motor has two sets of stator polepieces 16, 18 mounted with permanent magnet 28 and wound core 20 on a frame 26 and rotor 14 mounted on core 20 so that two magnetic circuits are formed with core 20 common to both. Rotor 14 is provided with equally spaced peripheral poles 46 co-operating with poles 22, 24 on stators 16, 18 respectively. Under the influence of the permanent magnet flux the rotor poles are aligned with poles 24 on stator 18 to provide a rest position. If coil 44 is energized the induced magnetic polarity of rotor 14 is changed and poles 46 are simultaneously attracted into alignment with poles 22 of stator 16 and repelled by poles 24 on stator 18. On de-energization of the coil, the rotor poles are attracted by poles 24 to complete the step. To ensure that rotor 14 rotates in one direction with constant torque the peripheral length of the stator polepieces reduces in the direction of rotation such that the polepieces at the extreme end of each set have the same width as the rotor polepieces. Other configurations may be used to give different torque characteristics, Figs. 8 and 9 (not shown). The rotor mounting may be modified to provide an annular air gap with the core, Fig. 7 (not shown). In the alternative construction, Figs. 10 and 11 (not shown), poles (314) of upper field plate (312) alternate with poles (318) of lower field plate (302) around rotor (290) and an annular magnet (296) is secured between the field plates. Rotor 296 is mounted on shaft (310) journalled in core (304) which carries a winding (294). In operation, energization of coil (294) causes rotor poles (316) to be attracted to poles (318) and, on subsequent de-energization the rotor poles are attracted to poles (314) (as shown in Fig. 11), the direction of rotation being ensured by rotor pole extension (330). In a modification, where the number of rotor poles is equal to the number of poles on one field plate, the width of the rotor poles varies to provide the correct direction of rotation and graded torque over the step, Fig. 14 (not shown).