Method of controlling a bi-directional stepping motor and a bi-directional stepping motor adapted to be controlled by this method

• US 5,028,857 A
• Filed: 05/10/1989
• Issued: 07/02/1991
• Est. Priority Date: 05/11/1988
• Status: Expired due to Fees

• Current Assignee: ETA SA Fabriques d'Ebauches
• Original Assignee: ETA SA Fabriques d'Ebauches
• Inventors: Taghezout, Daho
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): BERGMANN, SAUL
• Application Number:
  US07/349,727
• Time in Patent Office: 783 Days
• Field of Search: 318/696, 318/685, 368/157
• US Class Current: 318/696
• CPC Class Codes: G04C 3/14 incorporating a stepping motor G04C3/02 - G04C3/12 take precedence generating timing pulses G04F5/00, G04G3/00; setting G04G5/00; synchronisation G04G7/00; generating commutating pulses in masterclocks G04C13/0463, G04C13/02; slave clocks actuated intermittently by electromechanical step advancing mechanisms G04C13/10; control circuits for stepping motors in general H02P8/00
• CPC Class Codes: H02K 37/14 with magnets rotating within the armatures
• CPC Class Codes: H02P 8/02 specially adapted for single-phase or bi-pole stepper motors, e.g. watch-motors, clock-motors

Abstract

A method for improving the efficiency of a stepping motor (1) comprising a rotor (15) having a permanent magnet (16) producing a first magnetic field, as well as a first coil (13) and a second coil (14) for supplying to the magnet (16) respectively a second magnetic field (18) and a third magnetic field (19) symmetrical to one another in relation to an axis of symmetry (7) intersecting the axis of rotation (15a) of the rotor (15). The method comprises supplying to the motor (1), to make its rotor (15) turn in a given sense, drive pulses during which the two coils (13, 14) are supplied simultaneously by currents having a sense and an intensity such that, at the beginning of each drive pulse, the resultant magnetic field produced by the vectorial addition, in the magnet (16), of the second field (18) and the third field (19) forms, with another magnetic field (17) that results from the vectorial addition, in the magnet (16) of the two parts of the field produced by the latter magnet each of which flows through one of the coils (13, 14), an angle between 110° and 160° and having a sense, measured from the latter resultant field (17) towards the former, identical to the sense of rotation of the rotor (15). The claimed motor (1) may advantageously be controlled by this method due to the fact that its positioning means (21,22) are arranged such that, in each of the rest positions of the rotor (15), the aforesaid second resultant field (17) forms an angle (A) of from 20° to 70° with the axis of symmetry (7).

Claims

1. A method of controlling a stepping motor rotatable in both senses, said motor comprising :

a rotor comprising a permanent magnet producing a first magnetic field;

a first coil, traversed by a first part of said first magnetic field and intended to produce a second magnetic field in response to a first current;

a second coil, traversed by a second part of said first magnetic field and intended to produce a third magnetic field in response to a second current, said first and second parts of the first magnetic field forming in said permanent magnet a first resultant field; and

positioning means for maintaining said rotor in or for returning said rotor to any one of a plurality of rest positions;

said method comprising the production of said currents and the simultaneous supply thereof to the coils each time said rotor must turn by one step, said currents being produced with the same sense during the entire duration of their supply to said coils and with intensities such that, at the beginning of said current supply and when the rotor occupies one of said rest positions, said first resultant field forms an angle having a value between about 110° and

about 160°

with a second resultant field produced in said permanent magnet by said second and third magnetic fields, said senses of said currents being furthermore such that said angle has a sense, when measured from the first resultant magnetic field towards the second resultant magnetic field, which is the sense in which the rotor should turn.

2. The method of claim 1, wherein said angle is substantially equal to 135°

.

3. The method of claim 1, wherein said positioning means are arranged in such a manner that in each of said rest positions of the rotor said first resultant field makes, with a reference axis which is one of the axes of symmetry of the directions of said second and third magnetic fields in said permanent magnet, an angle substantially equal to 45°

,said first and second currents being produced with substantially equal intensities.

4. A stepping motor rotatable in both senses, comprising:

a rotor comprising a permanent magnet producing a first magnetic field;

a first coil for producing a second magnetic field and traversed by a first part of said first magnetic field;

a second coil for producing a third magnetic field and traversed by a second part of said first magnetic field said first and second parts of a first magnetic field forming in said permanent magnet a resultant magnetic field;

first means for applying said second magnetic field to said permanent magnet in a first direction;

second means for applying said third magnetic field to said permanent magnet in a second direction symmetrical to said first direction relative to an axis of symmetry; and

,

positioning means for maintaining said rotor in or for returning said rotor to any one of a plurality of rest positions, said positioning means being arranged in such a manner that, in each of said rest positions, the resultant magnetic field formed in said permanent magnet by said first and second parts of the first magnetic field makes angle from about 20°

to about 70°

with said axis of symmetry.

5. A stepping motor according to claim 4, wherein said angle is substantially equal to 45°

.

6. A stepping motor rotatable in both senses, comprising:

a rotor comprising a permanent magnet producing a first magnetic field;

a first coil for producing a second magnetic field in response to a first current and traversed by a first part of said first magnetic field;

a second coil for producing a third magnetic field in response to a second current and traversed by a second part of said first magnetic field, said first and second parts of the first magnetic field forming in said permanent magnet a first resultant field;

first means for applying said second magnetic field to said permanent magnet in first direction;

second means for applying said third magnetic field to said permanent magnet in a second direction symmetrical to said first direction relative to an axis of symmetry;

positioning means for maintaining said rotor in or for returning said rotor to any one of a plurality of rest positions; and

means for simultaneous supply of said currents to the coils each time said rotor must turn by one step, said currents being produced with the same sense during the entire duration of their supply to said coils and with intensities such that, at the beginning of said current supply and when the rotor occupies one of said rest positions, said first resultant field forms an angle having a value between about 110° and

about 160°

with a second resultant field produced in said permanent magnet by said second and third magnetic fields, said senses of said currents being furthermore such that said angle has a sense, when measured from the first resultant magnetic field towards the second resultant magnetic field, which is the sense in which the rotor should turn.

7. A stepping motor according to claim 6, wherein said positioning means is arranged in such a manner that, in each of said rest positions, the first resultant magnetic field formed in said permanent magnet by said first and second parts of the first magnetic field makes an angle from about 20°

to about 70°

with said axis of symmetry.

8. A stepping motor according to claim 7, wherein said angle with said axis of symmetry is substantially equal to 45°

.