CH716057A2 - Oscillator for electromechanical watch movement. - Google Patents

Abstract

The invention relates to an oscillator (10) of a regulating member for an electromechanical watch movement. The oscillator (10) comprises: a balance (12) comprising a balance shaft; a hairspring (16) comprising an inner end secured to the balance axis and an outer end secured to a pin (18), and a balance cage (20) comprising a first and a second pivot supporting the respective ends of the 'balance axis, the balance cage (20) being integral with the pin (18). The oscillator (10) further comprises a stepping motor, the rotor (30) of which is connected to the balance cage. The invention also relates to a method for maintaining the isochronism of the oscillations of the balance spring (12, 16) of the oscillator (10).

Description

Technical area

The present invention relates to an oscillator for an electromechanical watch movement, comprising a sprung balance, the oscillations of which are maintained by a step-by-step motor. The invention also relates to a regulating member comprising such an oscillator. The invention further relates to an electromechanical watch movement comprising such a regulator as well as a timepiece comprising the electromechanical watch movement. The invention also relates to a method for maintaining the isochronism of the oscillations of the balance spring of the oscillator.

State of the art

[0002] Electromechanical watch movements are already known comprising an oscillator of the sprung balance type, the oscillations of which are maintained by an electronic circuit.

[0003] By way of example, there are in particular watch movements comprising a sprung balance whose oscillations are maintained by an electromagnetic field. The balance comprises magnets mounted around the rim while micro-coils are arranged under the sprung balance. An electronic circuit controls the power supply to the micro-coils so as to impart an oscillating movement to the sprung balance.

[0004] Since traditional balance springs are sensitive to magnetic fields, the oscillations of the balance spring are affected by the electromagnetic field generated by the micro-coils, which has a negative impact on the precision of the movement.

[0005] Furthermore, it is known that the operation of an oscillator of the sprung balance type is strongly dependent on the operating amplitude of the oscillator.

[0006] However, the amplitude losses linked in particular to the losses of energy upstream of the oscillator, in particular to the loss of torque generated by the barrel when the barrel spring is disarmed, to the losses of energy at the level gears kinematically connecting the barrel and the escapement anchor, as well as the delay generated by the escapement, have a negative impact on the operation of the oscillator.

[0007] Operation at constant amplitude on the power reserve and by extension over a long period of operation makes it possible to improve the running of the watch.

Complications on the barrel and constant force mechanisms intended to overcome the problem of loss of torque when the barrel spring disarms, for example by a fusee-chain transmission, make it possible to approach an operation at amplitude constant.

[0009] It is also known that the operation of an oscillator of the sprung balance type is strongly dependent on the position of the oscillator. A tourbillon mechanism is an existing solution to compensate for the variations in rate resulting from the various positions of the oscillator.

The aforementioned mechanisms have the disadvantage of being complex and difficult to implement, which has a significant impact on the production costs of the watch movement and by extension on the price of a timepiece.

Furthermore, the energy losses at the level of the gears kinematically connecting the barrel and the anchor of the escapement as well as the delay generated by the escapement are difficult to compensate for.

An object of the present invention is therefore to provide an original alternative of an oscillator of the sprung balance type aimed at overcoming the aforementioned disadvantages.

[0013] More particularly, an aim of the present invention is to provide an oscillator suitable for maintaining the isochronism of the oscillations of the sprung balance over a long period of operation.

Another object of the present invention is to provide an oscillator which has the advantage of being easy to implement.

Another object of the invention is to provide a method for maintaining the isochronism of the oscillations of the balance spring of the oscillator.

Brief summary of the invention

[0016] These objects are achieved, according to one aspect of the invention, by an oscillator of a regulator member for an electromechanical watch movement, comprising: a balance comprising a balance axis; a hairspring comprising an inner end secured to the balance and an outer end secured to a stud, and a balance cage comprising a first and a second pivot supporting the respective ends of the balance shaft, the balance cage being integral with the eyebolt.

[0017] According to the invention, the oscillator further comprises a stepper motor, the rotor of which is connected to the balance cage.

According to one embodiment, the balance cage further comprises an axial opening opening into an axial housing in which the end of the rotor of the stepping motor is arranged.

[0019] According to one embodiment, the eyebolt is arranged in a bolt carrier integral with the balance cage.

[0020] According to one embodiment, the oscillator further comprises a racket for adjusting the active length of the hairspring. The racket is pivotally mounted on the balance cage relative to the eyebolt holder.

[0021] According to one embodiment, the balance cage comprises a first and a second part assembled against each other so as to form a frame within which the sprung balance is arranged.

According to one embodiment, one of said first and second parts has two opposite faces. One of the opposite faces has the axial opening opening onto the housing, while the other of said opposite faces has another housing in which is arranged one of said first and second pivots supporting one end of the axis of pendulum.

Another aspect of the invention relates to a regulating member for an electromechanical watch movement, comprising the oscillator as described above and an escapement, for example a Swiss escapement.

According to one embodiment, the regulating member is arranged in a tourbillon cage.

Another aspect of the invention relates to an electromechanical watch movement comprising the regulator member described above. The escapement of the regulating member is arranged to transmit the oscillation frequency of the oscillator to a display means, for example to an hour, minute and / or second hand.

Another aspect of the invention relates to a timepiece comprising the above electromechanical watch movement.

Another aspect of the invention relates to a method for maintaining the isochronism of the oscillations of the balance spring of the oscillator as described above. The method consists in controlling the stepping motor so that each step of the motor takes place within a time interval less than the duration of one alternation of the balance-spring of the oscillator.

[0028] According to one embodiment, the method consists in setting the frequency of the stepping motor on the frequency of the sprung balance or on a multiple of said frequency of the spring balance.

According to one embodiment, the method consists in controlling the stepper motor so that each step of the motor takes place alternately in one direction and in an opposite direction so as to print on the cage. balance wheel a back and forth movement the frequency of which corresponds to the running frequency of the sprung balance.

Brief description of the figures

An example of implementation of the invention is described in the description illustrated by the appended figures in which: <tb> <SEP> • FIG. 1 illustrates a perspective view of the oscillator according to an embodiment of the invention, <tb> <SEP> • Figure 2 illustrates a perspective view of the oscillator of Figure 1 engaged with an escape anchor, <tb> <SEP> • Figure 3 illustrates a sectional view of Figure 2 along an axial plane coinciding with the balance cage, and <tb> <SEP> • Figures 4a, 4b, and 4c illustrate top views of the oscillator according to different operating phases of a maintenance performed by a stepper motor.

Examples of embodiment of the invention

The oscillator 10 according to Figure 1 is adapted to be driven by a step-by-step motor in order to maintain the isochronism of the oscillations of the sprung balance 12, 16 over a long period of operation corresponding to the battery life or battery powering the stepper motor. The energy necessary to maintain the oscillations of the sprung balance 12, 16 has the particularity of being transmitted by the displacement of the point of equilibrium of the hairspring 16 by printing on the pin 18 in a back and forth movement unlike the conventional oscillators where energy is transmitted to the sprung balance via the fork of an anchor, in particular a Swiss anchor acting on the plate pin secured to the balance axis.

According to Figure 2, the oscillator is engaged with an escape anchor 50, for example a Swiss anchor, through the plate pin. The escape anchor 50 cooperates with an escape wheel (not shown), which is engaged with a set of gears in order to transmit information relating to the time to display means, for example to a hour, minute and / or second hand.

According to Figure 3, the balance 12 of the oscillator 10 is mounted on a balance shaft 14. The inner end of the hairspring 16 is integral with the balance shaft 14 while the outer end of the hairspring 16 is integral with the peg 18 (Figures 1 and 2). The oscillator 10 comprises a balance cage 20 comprising a first and a second pivot 21a, 21b in which the respective ends of the balance axis 14 are arranged.

According to Figure 1, the pin 18 is mounted in a pin holder 23 which is integral with the balance cage 20. The oscillator 10 further comprises a snowshoe system comprising a racket 24 for adjusting the active length of the hairspring in order to correct rate deviations during quality control during the manufacture of a watch movement comprising the oscillator 10 according to the invention.

The racket 24 comprises for this purpose an arm 25 supporting a pin 26 provided with a slot inside which a segment of the hairspring 16 is arranged. The racket 24 is adjusted with fat friction on the balance cage 20.

According to Figures 2 and 3, the balance cage 20 is in the form of a balance frame comprising a first and a second part 20a, 20b assembled against each other by a fixing system, by example by means of screws 32. The balance pin 14 is pivotally mounted inside the balance frame 20.

More particularly, according to Figure 3, the first part 20a of the balance frame 20 comprises a first and a second face 22a, 22b which are opposite. The first face 22a of the first part 20a of the balance frame 20 is provided with an axial opening opening onto a first housing 27 in which is mounted the end of the rotor 30 of the stepping motor so as to be able to drive in rotation of the balance frame 20. The second face 22b of the first part 20a of the balance frame 20 comprises a second housing 28 centered on the axial opening of the first housing 27 and in which is arranged the first pivot 21a supporting one end of the The balance axis 14. The other end of the balance axis 14 is mounted in the second pivot 21b, which is mounted on the second part 20b of the balance frame 20. A damper 40 is arranged against the second pivot 21b for attenuate shocks on the balance axis 14.

The oscillator 10 which has just been described makes it possible to maintain the isochronism of the oscillations of the sprung balance 12, 16 by rotating the balance cage 20 by means of the stepping motor.

The amplitude contribution provided by each jump of the stepper motor to the balance cage 20 makes it possible to compensate for the amplitude losses linked in particular to the energy losses of the oscillator.

An amplitude balance is a direct consequence of the amplitude of the step of the stepping motor and of the frequency at which the stepping motor takes each step. The greater the amplitude and frequency of each step of the motor, the greater the energy input and the amplitude of oscillation of the balance of the oscillator.

So that the oscillator 10 can maintain the isochronism of the oscillations of the balance wheel, different control modes of the stepper motor can be considered provided that each step of the motor takes place in a time interval less than the duration d 'an alternation of the balance and that the frequency of the motor is synchronized with the frequency of the oscillator or on a multiple of the latter.

In the case of an oscillator oscillating for example at a frequency of 4Hz, that is to say when an alternation of the balance is carried out every 125ms, the step-by-step motor must be controlled at a frequency greater than 4Hz so that each step takes place in a time interval less than 125ms.

Furthermore, the number of alternations performed by the balance between each step of the motor can be chosen freely. By way of example, for an oscillator oscillating at a frequency of 4Hz, the motor must be controlled so as to take a step every 250ms, 500ms, 750ms etc.

The stepper motor can also be driven so that it rotates one step in one direction then a rotation of one step in the opposite direction and so on in order to impart to the balance cage an oscillating movement fixed to the oscillation of the balance of the oscillator. For an oscillator oscillating for example at a frequency of 4Hz, the step-by-step motor is controlled to perform a rotation of one step in one direction, then 125ms (or 250 + 125ms or 500 + 125ms) later a rotation of 'a step in the opposite direction.

Figures 4a, 4b and 4c illustrate the different phases of the driving of the oscillator by the stepper motor. According to FIG. 4a, oscillator 10 is in an initial state at rest. When the motor is controlled to take a step of 20 °, the pin 18, which is integral with the balance cage 20, is moved by 20 °, which has the consequence of starting the oscillations of the spring balance 12, 16 of oscillator 10 (Figure 4b). The oscillations of the sprung balance continue around the new equilibrium position with an amplitude of 20 °. After a further step of the motor of 20 °, the equilibrium position of the balance spring of the oscillator is displaced by 40 ° in total. The sprung balance starts to oscillate with an amplitude of 40 °.

For the oscillator 10 according to the invention to operate at very high amplitude, the step-by-step motor must be controlled so as to take steps more frequently or else steps of greater amplitude. Since the sprung balance oscillator is known to be the most isochronous at 220 °, the stepping motor control signal can be easily optimized to apply this amplitude to the oscillator.

[0047] Various modifications and variations to the embodiments described will be apparent to those skilled in the art without departing from the scope of the invention as defined in the appended claims. For example, the frequency of the oscillator can be measured, for example by an optical sensor. The signal from the optical sensor is then processed by a frequency divider circuit in order to display the time by a digital display.

Claims (13)

1. Oscillator (10) of a regulating member for an electromechanical watch movement, comprising: - a balance (12) comprising a balance shaft (14); - a hairspring (16) comprising an inner end secured to the balance (12) and an outer end secured to a pin (18), and - a balance cage (20) comprising a first and a second pivot (21a, 21b) supporting the respective ends of the balance shaft (14), the balance cage (20) being integral with the eye (18), characterized in thatthe oscillator (10) further comprises a stepper motor whose rotor (30) is connected to the balance cage. 2. Oscillator (10) according to claim 1, characterized in that the balance cage (20) further comprises an axial opening opening onto an axial housing (27) in which the end of the rotor (30) of the stepper motor by step is arranged. 3. Oscillator (10) according to claim 1 or 2, characterized in that the stud (18) is arranged in a stud holder (23) integral with the balance cage (20). 4. Oscillator (10) according to one of the preceding claims, characterized in that it further comprises a racket (24) for adjusting the active length of the hairspring (16), the racket (24) being pivotally mounted on the balance cage (20) in relation to the eyebolt holder (23). 5. Oscillator (10) according to one of the preceding claims, characterized in that the balance cage (20) comprises a first and a second part (20a, 20b) assembled against each other so as to form a frame within which the sprung balance (12, 16) is arranged. 6. Oscillator (10) according to the preceding claim, characterized in that one of said first and second parts (20a, 20b) comprises two opposite faces (22a, 22b), one of the opposite faces comprising the axial opening opening out. on the housing (27), the other of said opposite faces comprising another housing (28) in which is arranged one of said first and second pivots (21a, 21b) supporting one of the ends of the balance axis ( 14). 7. Regulator for an electromechanical watch movement, comprising the oscillator (10) according to one of the preceding claims and an escapement, for example a Swiss escapement. 8. Regulator member according to claim 7, characterized in that the regulator member is arranged in a tourbillon cage. 9. Electromechanical watch movement comprising the regulator member according to claim 7 or 8, the escapement of the regulator member being arranged to transmit the oscillation frequency of the oscillator (10) to a display means, for example. to an hour, minute and / or second hand through a set of gears. 10. Timepiece comprising the electromechanical watch movement according to claim 9. 11. Method for maintaining the isochronism of the oscillations of the sprung balance (12, 16) of the oscillator (10) according to one of claims 1 to 6, consisting in controlling the stepper motor so that that each step of said motor takes place within a time interval shorter than the duration of an alternation of the sprung balance (12, 16) of the oscillator (10). 12. Method according to the preceding claim, consisting in setting the frequency of the stepping motor on the frequency of the sprung balance (12, 16) or on a multiple of said frequency of the sprung balance (12, 16). 13. Method according to claim 10 or 11, consisting in controlling the stepper motor so that each step of the motor takes place alternately in one direction and in an opposite direction so as to print on the balance cage ( 20) a back-and-forth movement the frequency of which corresponds to the running frequency of the sprung balance (12, 16).