Continuously rotating electric motor having a permanent magnet rotor

Patent metadata

Field	Value
Publication number	US-10985679-B2
Application number	US-201916687803-A
Country	US
Kind code	B2
Filing date	Nov 19, 2019
Priority date	Dec 6, 2018
Publication date	Apr 20, 2021
Grant date	Apr 20, 2021

Abstract

A continuously rotating electric motor includes a rotor provided with permanent magnets and a stator formed by two coils in which, when the rotor is rotating, two induced voltage signals (U B1 and U B2 ) are respectively generated, which signals have an electric phase shift φ where 5°≤φ≤90°, preferably 30°<φ<65°. The control device includes a circuit for detecting intersection times (T C ) at which values of the two induced voltage signals are substantially equal. The control device is arranged to generate electric driving pulses to rotate the rotor, which are respectively initiated at initiation times determined by respective intersection times, and such that the electric driving pulses can be applied to the two coils arranged in series. Preferably, the control device is arranged such that the initiation times of the electric driving pulses occur directly after detections of corresponding intersection times.

First claim

The invention claimed is:

1. A continuously rotating electric motor comprising:
a rotor equipped with permanent magnets and a stator formed by coils magnetically coupled with the permanent magnets; wherein the permanent magnets and the coils are arranged such that the coils define, relative to the induced voltage generated in each of these coils when the rotor is rotated, substantially a first phase and a second phase, such that the two induced voltage signals respectively generated in any two coils of said coils are either in phase, or substantially have an electric phase shift q which corresponds to the electric phase shift between the first phase and the second phase, this electric phase shift having a value of between five and ninety degrees included; in that the electric motor comprises a control device comprising a circuit for detecting intersection times at which a first induced voltage signal, generated by the rotor rotating in one or more coils belonging to the first phase, has a value that is substantially equal to that of a second induced voltage signal, generated by the rotor rotating in one or more coils belonging to the second phase, the first and second induced voltage signals thus having said electric phase shift therebetween; and wherein the control device is arranged so as to be able to generate electric driving pulses in order to rotate the rotor, which pulses are respectively initiated at initiation times determined by respective intersection times, the control device being arranged such that said electric driving pulses can be applied to a set of coils formed by at least one coil of the first phase and by at least one coil of the second phase, which are arranged in series at least during application of the electric driving pulses.

2. The electric motor according to claim 1 , wherein the electric phase shift φ has a value of between ten and ninety degrees included.

3. The electric motor according to claim 1 , wherein the electric phase shift φ has a value of between thirty and sixty-five degrees.

4. The electric motor according to claim 1 , wherein the control device further comprises at least one switch momentarily allowing the one or more coils generating said first induced voltage signal to be electrically isolated from the one or more coils generating said second induced voltage signal in order to allow said intersection times to be detected by the circuit for detecting; wherein the circuit for detecting comprises a comparator, the two inputs whereof are respectively connected to a first terminal of the one or more coils generating said first induced voltage signal and to a first terminal of the one or more coils generating said second induced voltage signal; and wherein the control device is arranged such that, during detection phases for detecting said intersection times, the two corresponding second terminals are momentarily connected via two respective switches to a reference voltage.

5. The electric motor according to claim 1 , wherein the control device is arranged such that said initiation times at which said electric driving pulses are initiated occur directly after detections of corresponding intersection times, whereby no time delay means is provided for the generation of these electric driving pulses subsequent to the detections of the corresponding intersection times.

6. The electric motor according to claim 1 , wherein the control device further comprises a comparator, the two inputs whereof are connected to two terminals of a coil or of a set of coils belonging to one of the first or second phases, so as to allow the direction of rotation of the rotor to be detected in association with the circuit for detecting intersection times.

7. The electric motor according to claim 1 , wherein the supply voltage applied, upon application of said electric driving pulses, through said at least one coil of the first phase and said at least one coil of the second phase, which are thus arranged in series, is provided such that it is greater than the maximum value of the sum of the induced voltages thereof and less than one hundred and fifty percent of this maximum value when the rotor is turning with a nominal angular speed.

8. The electric motor according to claim 1 , wherein the control device further comprises at least one switch arranged so as to allow at least one coil of the first phase and at least one coil of the second phase to be powered separately and selectively, the control device being arranged such that it can, during a start-up phase of the electric motor, firstly power one of the first or second phases in order to position the rotor, then the other of these first or second phases in order to cause the rotor to rotate in the desired direction.

9. The electric motor according to claim 1 , wherein the stator is formed by only two flat coils which respectively constitute the first and second phases, whereby the permanent magnets of the rotor have an alternating axial polarisation.

10. A watch movement comprising:
the electric motor according to claim 9 , wherein the two coils are arranged in a same general plane, perpendicular to the rotational axis of the rotor, so as to occupy an angular sector, relative to the rotational axis of the rotor, of less than 230° to allow a wheel for transmitting the rotational movement of the rotor to be arranged in this general plane, the rotor comprising, for this purpose, a pinion arranged at said general plane and the central axis whereof is aligned with the rotational axis of the rotor.

Assignees

• Swatch Group Res & Dev Ltd

Inventors

• Born Jean-Jacques
• Nagy Laurent
• Germiquet Christophe

Classifications

• H02P2207/00

  Indexing scheme relating to controlling arrangements characterised by the type of motor · CPC title

• H02K37/10 Primary

  of permanent magnet type (H02K37/02 takes precedence) · CPC title

• H02P8/02

  specially adapted for single-phase or bi-pole stepper motors, e.g. watch-motors, clock-motors · CPC title

• G04C3/16

  incorporating an electro-dynamic continuously rotating motor (G04C3/02 - G04C3/12 take precedence) · CPC title

• H02P7/00 Primary

  Arrangements for regulating or controlling the speed or torque of electric DC motors · CPC title