Structure of stepping motor and method of driving the stepping motor

DETAILED DESCRIPTION An object of a first aspect of the present invention to solve the problem in the first conventional technique is to provide a hybrid stepping motor in which the electrical time constant is reduced without lowering the thrust constant by optimizing the position and form of permanent magnets used in the motor.
The foregoing object of the invention is attained by a structure of the stepping motor in which each permanent magnet is provided to face the gap of a stator or a movable member, the polarity of poles of the permanent magnet is inverted at a pitch equal to that of the teeth of the movable member or the stator facing the permanent magnet, and slots are provided in the permanent magnet at positions where the polarity of poles of the permanent magnet is changed over.
In the aforementioned structure in which the polarity of poles of the permanent magnet is inverted at a pitch equal to that of the teeth of the movable member or the stator facing the permanent magnet, the following operations are attained.
In a first condition in which the phase of the permanent magnet is made coincident with that of the teeth, the flux of the poles of the permanent magnet at the short gap length side (at the low gap magnetic reluctance side) is interlinked with the windings.
In a second condition in which the phase of the permanent magnet is shifted by half a pitch relative to that of the teeth, the gap magnetic reluctance is equal to the poles different in polarity of the permanent magnet so that the flux is terminated between the poles different in polarity of the permanent magnet and is not interlinked with the windings.
In a third condition in which the gap length for the poles of the permanent magnet is reversed to the first condition, the flux in the reverse direction to the first condition is interlinked with the windings.
As described above, the flux interlinkage with the windings which is zero in the first condition widely changes corresponding to the relative positional change of the permanent magnet on the basis of the condition where the flux interlinkage with the windings is zero