Stepping motor, method of driving the same and drive circuit therefor

• US 4,803,389 A
• Filed: 07/17/1987
• Issued: 02/07/1989
• Est. Priority Date: 07/22/1986
• Status: Expired due to Term

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Ogawa, Shigeki, Tsukada, Eiichi
• Primary Examiner(s): Salce, Patrick R.
• Assistant Examiner(s): Jones, Judson H.
• Application Number:
  US07/074,823
• Time in Patent Office: 571 Days
• Field of Search: 310/49 R, 310/154, 310/156, 310/190, 310/268, 310/DIG. 6, 318/254, 318/685, 318/696
• US Class Current: 310/49.55
• CPC Class Codes: H02K 29/08 using magnetic effect devices, e.g. Hall-plates, magneto-resistors H02K29/12 takes precedence
• CPC Class Codes: H02K 37/125 Magnet axially facing armature

Abstract

A stepping motor includes a first element including at least two permanent magnets each having a pair of N and S poles and a second element including a yoke arranged to be separated from the first element by a predetermined interval. The first and second elements can be moved relative to each other. The second element has a two-phase coil arranged on the yoke in association with a width of each pole in a moving direction of the permanent magnet and detent torque generating means for generating a static detent torque by relative movement. The detent torque generating means is arranged on the yoke such that a stable position of one of the first and second elements moved by a dynamic torque generated when one of the coils constituting the two-phase coil is energized is deviated from a stable position of a moving element caused by a detent torque generated from the detent torque generating means. A method of controlling the stepping motor is also disclosed.

Claims

1. A stepping motor comprising:

a first element including at least two permanent magnets each having a pair of N and S poles;

a second element including a yoke separated from said first element by a predetermined interval;

said first and second elements being relatively movable;

said second element including a two-phase coil arranged on said yoke at spaced locations corresponding to the relative spacing between said at least two permanent magnets, and means for generatin a static detent torque between said first and second elements at predetermined locations along the direction of movement diffusion from the locations of the detent torque due to the interaction between the magnetic field generated by the permanent magnets and the magnetic field generated by the coil when energized so that said first and second elements achieve a stable static detent position at one of said predetermined locations when the coil is de-energized;

means for supplying a drive current to one of the coils of said two-phase coil; and

means for supplying said drive current to the other coil of said two-phase coil after said two-phase coil is energized.

2. A motor according to claim 1, wherein

said first element comprises a rotor, and said second element comprises a stator.

3. A motor according to claim 1, wherein

said two-phase coil comprises a plurality of individual coils each having a shape corresponding to the shape of at least one of said permanent magnets and each has an axis perpendicular to the direction of movement of said first and second elements.

4. A motor according to claim 3, wherein

said magnets are offset from the corresponding ones of said individual coils along the direction of movement when said first and second elements are in a stable static detent position.

5. A motor according to claim 1, wherein

said detent torque generating means includes means for providing a predetermined variation to the magnetic reluctance of said yoke along the length thereof.

6. A motor according to claim 1, further comprising:

polarity detecting means, arranged between said first and second elements, for detecting the polarity of the permanent magnet adjacent thereto; and

means for energizing one of the coils of said two-phase coil in accordance with a detected polarity, thereby moving the movable one of the relatively movable elements to the next stable position provided by the static detent torque generating means.