Linear stepping motor

Claim 1

A linear stepping motor comprising: an elongated stationary member having a plurality of teeth arranged at a pitch τ transversely of a longitudinal direction of said stationary member; a movable member having first, second, third and fourth pole pieces arranged in the order named in said longitudinal direction of said stationary member, each of said pole pieces having a plurality of teeth opposed to said teeth of the stationary member and arranged at the pitch τ, wherein said teeth of the second pole piece are located apart by lτ+1/2τ, those of the third pole piece are located apart by mτ±1/2τ, and those of the fourth pole piece are located apart by nτ±1/4τ from the respective teeth of the first pole piece, in which l, m and n are integers; attraction magnetic pole means for maintaining said movable member floated by a magnetic coil providing an attractive force of a magnetic flux passing through a body of the movable member, between the first and the second pole pieces, a tooth portion of the stationary member, a body of the stationary member, between the third and the fourth pole pieces, and said body of the movable member; guiding magnetic pole means comprising first, second, third and fourth magnetic coils wound on the first, the second, the third and the fourth pole pieces, respectively; guiding control means for controlling said guiding magnetic pole means to consecutively selectively energize said first to fourth magnetic coils in a predetermined order such that the teeth of the pole piece on which the energized magnetic coil is wound align with the teeth of the stationary member, and thereby to cause the movable member to move in the longitudinal direction of the stationary member; and gap control means for maintaining a gap between said stationary member and said movable member constant during the movement of the movable member.