Vibration motors, especially those used in watch movements

Abstract

To provide a vibration motor for watch movements with reduced power consumption. [Solution] The motor 1 comprises a rotor 2 equipped with magnets and a stator 3 equipped with at least one coil that enables the rotation of the rotor, the rotor being rotatably movable relative to the stator by vibration between two extreme positions when actuated by the coil, and elastic return means that returns the rotor between the extreme position and an intermediate resting position when the rotor is no longer actuated by the coil, the motor functions by the rotational oscillating motion of the rotor to produce each step.

Description

Technical Field

[0001] The present invention relates to the field of stepping motors, particularly to horology. More specifically, the present invention relates to vibrating motors or oscillating motors.

Background Art

[0002] In most electronic watch movements, the energy required to rotate the hands (e.g., the second hand, minute hand, and hour hand) is supplied by a stepping motor such as a Lavet motor.

[0003] These single-phase motors have a rotor that rotates in steps, rotating half a turn relative to the stator for each step, defining each second. At each step, the rotor drives a gear train within the watch movement, and this gear train drives the hands. The step rate is generally determined by a time base comprising a crystal oscillator.

[0004] When the motor is operating, the positioning torque holds the rotor in a given position, and the magnet-coil coupling enables the rotor to rotate between these positions. However, since the coupling is a sine function of the rotor position, a decrease in efficiency is observed over part of the rotation.

[0005] The rotor is also mounted on bearings so as to be able to rotate. However, this type of assembly causes friction between the shaft ends of the rotor and the bearings. This friction is caused by the weight of the rotor, the lateral attractive force of the rotor magnet, and the contact between the gear train of the movement and the rotor pinion when the gear train is driven by the rotor.

[0006] As a result, these problems cause energy losses and thus an increase in power consumption compared to what is necessary for the motor to operate efficiently.

Summary of the Invention

[0007] The object of the present invention is to eliminate all or part of the drawbacks described above by providing a motor that consumes less power compared to a ravet motor.

[0008] For this purpose, the present invention relates in particular to a vibration motor for a watch movement, the motor comprising a rotor having a magnet and a stator having at least one coil, the coil enabling the rotation of the rotor to be actuated in steps, the rotor being rotatably movable relative to the stator by vibration between two angular extreme positions when actuated by the coil.

[0009] A notable feature of the present invention is that the motor includes elastic return means for returning the rotor between an extreme position and an intermediate resting position when the rotor is no longer actuated by the coil, and the motor is actuated by the rotational oscillating motion of the rotor to generate each step.

[0010] The motor operates by the rotational oscillating motion of the rotor between two extreme positions at the resonant frequency, in order to generate each step of the motor. In this way, the motor reciprocates, which causes the motor to move incrementally forward.

[0011] Such motors allow for a reduction in the angular displacement of the rotor compared to single-phase ravet motors, thereby making the electromagnetic coupling between the magnets and coils more efficient. This is because the coupling lies around the maximum value of the sine function of the coupling.

[0012] Furthermore, since the rotor is rotationally guided by the elastic return mechanism instead of bearings, friction between the rotor shaft and the bearings holding the rotor shaft is avoided.

[0013] According to the present invention, energy loss is reduced, and consequently, the power consumption of the motor is reduced, for example, by half in the case of a certain motor.

[0014] According to a particular embodiment of the present invention, the elastic return means comprises a flexible guide positioned to suspend the rotor from the stator.

[0015] According to a particular embodiment of the present invention, the flexible guide comprises an upper flexible portion that connects the upper part of the rotor above the stator and a lower flexible portion that connects the lower part of the rotor below the stator.

[0016] According to a particular embodiment of the present invention, the upper and / or lower flexible portion of the flexible guide comprises at least one pair of non-intersecting flexible blades, preferably two pairs of parallel-arranged non-intersecting flexible blades.

[0017] According to certain embodiments of the present invention, the upper and / or lower flexible portion of the flexible guide comprises at least one individual flexible blade, preferably two individual flexible blades arranged in parallel.

[0018] According to a particular embodiment of the present invention, the flexible guide comprises a fixed element integrally attached to the stator and a movable element integrally attached to the rotor, wherein the fixed element and the movable element are connected by a flexible blade on the flexible guide.

[0019] According to a particular embodiment of the present invention, the flexible guide comprises an intermediate arched section arranged around the rotation axis of the rotor, and two pairs of flexible blades connect the intermediate arched section to a movable element by a first pair of flexible blades and the intermediate arched section to a fixed element by the other pair of flexible blades.

[0020] According to a particular embodiment of the present invention, two pairs of flexible blades are arranged symmetrically on both sides of the intermediate arched portion.

[0021] According to a particular embodiment of the present invention, the flexible guide comprises a central arched section arranged around the rotation axis of the rotor, and a single flexible blade connects the central arched section to a movable element by a first single flexible blade and the central arched section to a fixed element by the other single flexible blade.

[0022] According to a particular embodiment of the present invention, the motor comprises a meshing pinion for meshing with a gear train, particularly a gear train in a watch movement, the meshing pinion being rotatably mounted above the rotor.

[0023] According to a particular embodiment of the present invention, the motor comprises a wheel with a check click, and a movable click mounted on the rotor and a fixed click mounted on the stator.

[0024] According to a particular embodiment of the present invention, the meshing pinion and click wheel are mounted on the rotor in a first rotational direction of the rotor, and are mounted so as to be able to rotate freely around the axis of rotation of the rotor in a second rotational direction of the rotor.

[0025] According to a particular embodiment of the present invention, when the rotor vibrates between two extreme positions, the click wheel is driven by a movable click to rotate with the rotor in one direction relative to the stator during each vibration period of the rotor when the rotor rotates in one direction, and is held by a fixed click when the rotor rotates in the opposite direction.

[0026] According to a particular embodiment of the present invention, the total rotation angle between the extreme positions is less than half a turn, preferably less than a quarter turn, and even less than an eighth turn, so as to oscillate near the maximum value of the magnet-coil torque.

[0027] According to a particular embodiment of the present invention, when in the resting position, the magnetization vector of the magnet is oriented so as to be substantially perpendicular to the principal axis of the magnetic flux f generated by the coil in order to obtain the maximum magnet-coil torque.

[0028] According to a specific embodiment of the present invention, the motor is configured to vibrate at its natural frequency so as to minimize power consumption, and the natural frequency is determined particularly by the inertia of the rotor and the inertia of the elastic return means.

[0029] The present invention also relates to a timepiece movement provided with such a vibrating motor.

Brief Description of the Drawings

[0030] The objects, advantages, and features of the present invention will become apparent by reading some embodiments provided only as non-limiting examples with reference to the accompanying drawings. [Figure 1] FIG. 1 schematically shows a partial perspective view of a vibrating motor according to a first embodiment of the present invention, particularly for a timepiece movement. [Figure 2] FIG. 2 schematically shows a partial top view of the vibrating motor of FIG. 1. [Figure 3] FIG. 3 schematically shows a cross-sectional view of a vibrating motor according to a second embodiment of the present invention. [Figure 4] FIG. 4 schematically shows a top view of the vibrating motor of FIG. 3. [Figure 5] FIGS. 5a and 5b show two steps in the operation of a click wheel. [Figure 6] FIG. 6 is a graphical representation of the timing of a vibrating motor according to the present invention. [Figure 7] FIG. 7 schematically shows the magnets and coils of a motor according to the present invention. [Figure 8] FIG. 8 is a graph showing the magnet-coil torque according to the rotor angle in a vibrating motor according to the present invention.

Mode for Carrying Out the Invention

[0031] Figures 1 and 2 show a schematic representation of a first embodiment of the vibration motor 1 according to the present invention, having a cross arrangement of flexible blades on a flexible guide. Such a motor 1 can be used, for example, as an actuator in a watch movement, and in particular to drive a gear train that operates a display device, such as the hands.

[0032] Motor 1 comprises a rotor 2 and a stator 3, the rotor 2 being rotatably mounted inside a fixed stator 3. The rotor 2 comprises permanent magnets and a cylindrical body, which is generally a resin overmolding of the permanent magnets. The stator 3 comprises a body with a circular through-opening that allows the rotor 2 to be placed inside. The stator 3 comprises one or more coils for acting as a mechanism for rotating the rotor 2.

[0033] On the one hand, the rotor 2 includes a shaft 12 that extends axially above the cylindrical body from axial disks positioned above and below the cylinder of the rotor 2.

[0034] The motor 1 also includes a meshing pinion 15 attached to the rotor 2. The meshing pinion 15 is rotatably fixed to the rotor 2, particularly in the first direction of rotation of the rotor 2, but is also mounted to be freely rotatable about a shaft 12 that extends axially over the cylindrical body of the rotor 2, particularly in the second direction of rotation of the rotor 2.

[0035] Such a meshing pinion 15 can mesh with, for example, a gear train in a watch movement (not shown).

[0036] The meshing pinion 15 is rotatably movable relative to the stator 3 in a first direction when the rotor 2 is actuated by the coil and vibrates between two extreme positions.

[0037] Therefore, motor 1 operates to generate each step of motor 1 by rotational oscillating motion between two extreme positions of rotor 2.

[0038] To this end, according to the present invention, the motor 1 includes elastic return means for returning the rotor 2 from the extreme position to the rest position when the rotor 2 is no longer actuated by the coil. Preferably, the rest position is located midway between the extreme positions.

[0039] The return mechanism includes a flexible guide 5 that suspends the rotor 2 and is positioned to guide the rotor 2's rotation, and further provides a force to return the rotor 2 to its resting position.

[0040] The flexible guide 5 comprises a fixed element 27 attached to the stator 3 and a movable element 28 attached to the rotor 2, and the fixed element 27 and the movable element 28 are connected by an elastic return means.

[0041] In this case, the fixed element 27 comprises two plates 7 and 8 that are mounted on top of the stator 3, with the first plate 7 located above the stator 3 and the second plate 8 located below the stator 3.

[0042] In the so-called cross-shaped first embodiment shown in Figures 1 and 2, the movable element comprises two partially open disc portions 9 and 11, one portion 9 positioned above the rotor 2 and the other portion 11 positioned below the rotor 2. Each disc portion 9 and 11 is connected to the rotor 2 and comprises two inner blade pieces 16 connected to each other by a curved portion 17.

[0043] The flexible guide 5 comprises an upper flexible portion 14 that connects the upper part of the rotor 2 above the stator 3 and a lower flexible portion 19 that connects the lower part of the rotor 2 below the stator 3.

[0044] Preferably, the upper flexible portion 14 and the lower flexible portion 19 are substantially the same.

[0045] The upper flexible section 14 and / or the lower flexible section 19 comprises at least one pair of non-intersecting flexible blades 20, preferably two pairs of non-intersecting flexible blades 20, 21, which are positioned above the rotor 2.

[0046] The two pairs of flexible blades 20 and 21 are connected by an intermediate arched section 13 positioned around the axis 12 of the rotor 2, and the two pairs of flexible blades 20 and 21 are arranged symmetrically on both sides of the intermediate arched section 13. Thus, the first pair of flexible blades 20 connects the intermediate arched section 13 to a stationary element, in this case to the upper plate 7 or the lower plate 8, and the second pair of flexible blades 21 connects the intermediate arched section 13 to a movable element, in this case to the disc section 9.

[0047] Figures 3 and 4 show a second embodiment of the motor 1 according to the present invention, which has a different arrangement of the flexible blades of the flexible guide 5, a so-called in-line arrangement. There are no functional differences between these embodiments, and both enable the rotor 2 to rotate and guide.

[0048] The upper flexible portion 14 and / or lower flexible portion 19 of the flexible guide 5 are provided with at least two parallel-arranged flexible blades 22, 23. The two flexible blades 22, 23 are symmetrically arranged on the rotor 2, each connected on one side to a central arched portion 24 concentrically mounted on or below the rotor 2, and on the other side to the upper plate 7 or lower plate 8 of the stationary element 27 by the two pairs of flexible blades 19.

[0049] The two flexible blades 22 and 23 are substantially collinear when the rotor 2 is in the resting position.

[0050] Therefore, in both embodiments, the flexible guide 5 returns the rotor 2 from the extreme position to the resting position when the rotor 2 is no longer actuated by the coil.

[0051] The flexible blades on the flexible guide 5 are substantially straight when the rotor 2 is in the resting position of the flexible guide 5. On the other hand, when in the operating position, the blades on the flexible guide 5 are curved because they are subjected to stress due to the position of the rotor 2 relative to the stator 3.

[0052] Preferably, in order to ensure the efficiency of the magnet-coil coupling, the angular displacement of the rotor 2 is selected to be less than half a turn, or even less than a quarter turn or an eighth turn, as described below.

[0053] In Figures 4 and 5, the motor 1 also includes a check click wheel 25, which is attached to the meshing pinion 15 so as to hold the meshing pinion 15 in a second direction of rotation of the rotor. Preferably, the click wheel 25 is located only in the upper flexible portion 14 of the motor.

[0054] In this case, two fixed clicks 26f are positioned on the upper flexible portion 14 and are integrated with the stator 3, and in particular, are attached to the upper plate 8 of the stator 3. The fixed clicks 26f lock the reverse click wheel 25 in one direction.

[0055] The movable click 26m is attached to the rotor 2 and is configured to rotate together with the rotor 2.

[0056] The meshing pinion 15 and click wheel 25 are mounted on the rotor 2 in the first direction of rotation of the rotor 2, and are mounted so as to be freely rotatable around the rotation axis 12 on the rotor 2 in the second direction of rotation of the rotor 2.

[0057] The operation of motor 1, particularly the operation of click wheel 25, is shown in Figure 5. When rotor 2 vibrates, rotor 2 moves back and forth according to a sine function of time.

[0058] During the forward movement A in the first direction, the click wheel 25, and therefore the meshing pinion 15, is driven by the movable click 26m and rotates with the rotor 2 relative to the stator 3, while the fixed click 26f is reset by the rotation of the click wheel 25. Thus, the click wheel 25 moves one step.

[0059] During the second reverse movement B, the click wheel 25 is held by the fixed click 26f, while the movable click 26m is reset as a result of the click wheel 25 being held. During the reverse movement, the click wheel 25 is therefore stationary. In this way, the click wheel 25 takes a step of one tooth for each oscillation period of the rotor 2.

[0060] The meshing pinion 15 follows the movement of the click wheel 25. Therefore, it rotates in a step-like manner in the same direction.

[0061] In the graph of Figure 6, the first function F(2) represents the oscillation q of rotor 2 as a function of time. The second function F(25) represents the rotation of click wheel 25 as a function of time. Due to click 26, click wheel 25 continues to rotate in the same direction despite the return of rotor 2. Therefore, function F(25) increases by one level for each oscillation of rotor 2 in one direction.

[0062] Figure 7 shows a more general diagram of the motor 1. The stator 3 is substantially square and arch-shaped (frame-shaped), with one side having a support for the rotor 2 and a coil 31 wound around at least a portion of the other side of the stator 3. The rotor 2 is positioned within the support and includes a magnet 32.

[0063] When coil 31 is activated, rotor 2 oscillates between two limit positions, angle -q0 and +q0, around the 0° angle corresponding to the resting position.

[0064] The torque of motor 1 as a function of rotation angle q is shown in Figure 6. When rotor 2 is in the resting position (q=0), the magnetization vector of magnet 2 is oriented substantially perpendicular to the principal axis of the magnetic flux f generated by coil 31 in stator 3. When motor 1 is powered by an AC voltage, rotor 2 oscillates between two extreme positions -q0 and +q0.

[0065] This angular range ideally covers a total angle of less than half a turn, preferably a quarter turn, and even less than an eighth turn. In this case, the limit position is close to the maximum value of the magnet-coil torque, resulting in high electromechanical efficiency in such a motor 1.

[0066] Preferably, the motor 1 is configured to vibrate at its natural frequency in order to minimize power consumption. Its natural frequency is determined by the inertia of the rotor 2 and the elastic return mechanism.

[0067] Naturally, the present invention is not limited to the embodiment of the vibration motor described with reference to the drawings, and modifications can be envisioned without departing from the scope of the present invention.

Claims

1. A vibration motor (1) particularly for a watch movement, the vibration motor (1) comprises a rotor (2) having a magnet (32) and a stator (3) having at least one coil (31) that enables the rotation of the rotor (2), the rotor (2) being rotatable relative to the stator (3) by vibration between two extreme positions when actuated by the coil (31), and elastic return means for returning the rotor between the extreme position and an intermediate resting position when the rotor (2) is no longer actuated by the coil (31), the vibration motor (1) is operated by the rotational vibration motion of the rotor (2) to produce each step.

2. The vibration motor according to claim 1, wherein the elastic return means comprises a flexible guide (5) arranged to suspend the rotor (2) from the stator (3).

3. The vibration motor according to claim 2, wherein the flexible guide (5) comprises an upper flexible portion (14) that connects the upper part of the rotor (2) above the stator (3) and a lower flexible portion (19) that connects the lower part of the rotor (2) below the stator (3).

4. The vibration motor according to claim 3, wherein the upper flexible portion (14) and / or the lower flexible portion (19) of the flexible guide (5) comprises at least one pair of non-intersecting flexible blades (20), preferably two pairs of non-intersecting flexible blades (20, 21) arranged in series.

5. The vibration motor according to claim 2, wherein the upper flexible portion (14) and / or the lower flexible portion (19) of the flexible guide (5) comprises at least one individual flexible blade (22), preferably two individual flexible blades (22, 23) arranged in the same straight line on both sides of the arched portion.

6. The vibration motor according to claim 4, wherein the flexible guide (5) comprises a stationary element (27) attached to the stator (3) and a movable element (28) attached to the rotor (2), and the stationary element (27) and the movable element (28) are connected by the flexible blades of the flexible guide (5).

7. The vibration motor according to claim 6, wherein the flexible guide (5) comprises an intermediate arched portion (13) positioned around the rotation axis (12) of the rotor (2), and the two pairs of flexible blades (20, 21) connect the intermediate arched portion (13) to the movable element (28) by the first pair of flexible blades (20), and connect the intermediate arched portion (13) to the stationary element (27) by the other pair of flexible blades (21).

8. The vibration motor according to claim 7, wherein the two pairs of flexible blades (20, 21) are arranged symmetrically on both sides of the intermediate arch-shaped portion (13).

9. The vibration motor according to claim 5, wherein the flexible guide (5) comprises a stationary element (27) attached to the stator (3) and a movable element (28) attached to the rotor (2), the stationary element (27) and the movable element (28) are connected by the flexible blades of the flexible guide (5), the flexible guide (5) comprises a central arched portion (24) arranged around the rotation axis of the rotor (2), and the individual flexible blades connect the central arched portion (24) to the movable element by a first individual flexible blade (20) and connect the central arched portion (24) to the stationary element (27) by the other individual flexible blade.

10. The vibration motor according to claim 1, wherein the motor (1) comprises a meshing pinion (15) for meshing with a gear train, particularly a gear train in the watch movement, and the meshing pinion (15) is rotatably mounted above the rotor (2).

11. A vibration motor according to claim 10, comprising a wheel (25) equipped with a reverse click, the wheel (25) attached to the meshing pinion (15), a movable click (26m) attached to the rotor (2), and a fixed click (26f) attached to the stator (2).

12. The vibration motor according to claim 11, wherein the meshing pinion (15) and the click wheel (25) are mounted on the rotor (2) in a first rotational direction of the rotor (2) and are mounted so as to be freely rotatable around the rotation axis (12) of the rotor (2) in a second rotational direction of the rotor (2).

13. When the rotor (2) vibrates between two extreme positions, the click wheel (25) is driven by the movable click (26m) to rotate in one direction with the rotor (2) relative to the stator (3) during each vibration period of the rotor (2). On the other hand, when the rotor (2) rotates in the opposite direction, it is held in place by the fixed click (26f), as described in claim 12.

14. The vibration motor according to claim 1, wherein the total rotation angle between the extreme positions is less than half a turn, preferably less than a quarter turn, and moreover less than an eighth turn, so that it vibrates near the maximum magnet-coil torque.

15. The vibration motor according to claim 1, wherein, when in the resting position, the magnetization vector of the magnet (32) is directed substantially perpendicular to the principal axis of the magnetic flux f generated by the coil (31) in order to obtain the maximum magnet-coil torque.

16. The vibration motor according to claim 1, configured to vibrate at its natural frequency to minimize power consumption, wherein the natural frequency is determined in particular by the inertia of the rotor (2) and the inertia of the elastic return means.

17. A clock movement comprising a vibration motor (1) according to any one of claims 1 to 16.

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