초록 ▼

A linear stepper motor is provided with a feature to cause it to return to a zero position when current is cut off. The motor is formed of a stator armature assembly and a permanent magnet rotor assembly with poles thereof facing poles of the stator armature. The rotor assembly includes a rotor core

A linear stepper motor is provided with a feature to cause it to return to a zero position when current is cut off. The motor is formed of a stator armature assembly and a permanent magnet rotor assembly with poles thereof facing poles of the stator armature. The rotor assembly includes a rotor core formed as a nut with an axial threaded aperture extending therethrough. A shaft assembly includes a shaft screw mating with the rotor core nut, a front shaft affixed thereto, and a fixed sleeve overfitting the front shaft to permit axial motion thereof. A ball-and-groove arrangement in the front shaft and the sleeve prevents rotation of the shaft without impairing axial movement thereof. A spring causes return of the shaft to zero when there is no current applied to the stator armature. The spring can, for example, be a coil compression spring overfitting a portion of the shaft or a spiral torsion spring extending between the rotor and the stator armature.

대표청구항 ▼

A stepper motor comprising a stator assembly having first and second toroidal stator electromagnets each having a plurality 2n of evenly spaced axial teeth forming alternating salient stator poles, the stator poles of the first and second stator electromagnets being offset from one another by an ele

A stepper motor comprising a stator assembly having first and second toroidal stator electromagnets each having a plurality 2n of evenly spaced axial teeth forming alternating salient stator poles, the stator poles of the first and second stator electromagnets being offset from one another by an electrical angle of 90°; a permanent-magnet rotor having a rotor magnet with a plurality n of pairs of poles thereon arranged to face said stator poles, a rotor core supporting said rotor magnet and having a threaded central axial aperture, and bearing means mounting said rotor core for rotation relative to said stator electromagnets; an axially movable shaft assembly including a threaded screw disposed in said axial aperture and adapted to mate therewith, and engaging means engaging a longitudinal track on said shaft assembly for preventing relative rotation of said screw and said rotor assembly while permitting axial movement of said screw, at least to a limited extent; and means urging said screw to a zero axial position thereof whenever no current is applied to said stator electromagnet wherein the central axial aperture of the core and the threaded screw have a thread pitch selected to be low enough to permit rotation of said rotor to advance said shaft assembly when stepping current is applied to said stator electromagnets, but steep enough to permit force of said urging means to return said shaft assembly to said zero axial position when no current is applied to said electromagnets.