Patent Application
20180181073
This application claims priority from European Patent Applications No. 16206778.9 filed on Dec. 23, 2016 and Ser. No. 17/172,554.2 filed on May 23, 2017, the entire disclosures of which are incorporated herein by reference.
The present invention relates to a timepiece assembly, particularly a precision timepiece, comprising:
In particular, the mechanical resonator is a balance-hairspring and the maintenance device comprises a conventional escapement, for example having a Swiss pallet assembly. The auxiliary oscillator is formed particularly by a quartz resonator or by a resonator integrated in an electronic circuit.
Movements forming timepiece assemblies as defined in the field of the invention have been proposed in some prior documents. The patent CH 597 636, published in 1977, proposes such a movement with reference to
The electronic circuit comprises a time base comprising a quartz generator and serving to generate a reference frequency signal FR, this reference frequency being compared with the frequency FG of the mechanical oscillator. The frequency FG of the oscillator is detected via the electrical signals generated in the coil by the pair of magnets. The regulating circuit is suitable for momentarily inducing a braking torque via a magnetic magnet-coil coupling and a switchable load connected to the coil. The document CH 597 636 provides the following teaching: “The resonator formed should have a variable oscillation frequency according to the amplitude on either side of the frequency FR (isochronism error)”. It is therefore taught that a variation in the oscillation frequency of a non-isochronous resonator is obtained by varying the oscillation amplitude thereof. An analogy is made between the oscillation amplitude of a resonator and the angular velocity of a generator comprising a rotor equipped with magnets and arranged in a gear train of the timepiece movement in order to regulate the operation thereof. As a braking torque reduces the rotational speed of such a generator and as such the rotational frequency thereof, it is herein merely envisaged to be able to reduce the oscillation frequency of an obligatorily non-isochronous resonator by applying a braking torque reducing the oscillation amplitude thereof.
To perform electronic regulation of the frequency of the generator, or of the mechanical oscillator, it is envisaged in a given embodiment that the load is formed by a switchable rectifier via a transistor which loads a storage capacity during braking pulses, to retrieve the electricity so as to supply the electronic circuit. The consistent teaching given in the document CH 597 636 is as follows: When FG>FR the transistor is conductive; a power Pa is then drawn from the generator/oscillator. When FG<FR, the transistor is non-conductive; therefore, power is no longer drawn from the generator/oscillator. In other words, regulation is merely performed when the frequency of the generator/of the oscillator is greater than the reference frequency FR. This regulation consists of braking the generator/oscillator with the aim of reducing the frequency FG thereof. As such, in the case of the mechanical oscillator, those skilled in the art understand that regulation is only possible when the barrel spring is strongly armed and that the free oscillation frequency (natural frequency) is greater than the reference frequency FR, resulting from a voluntary isochronism error of the selected mechanical oscillator. Therefore, there is a two-fold problem, i.e. the mechanical oscillator is selected for that which is usually an error in a mechanical movement and the electronic regulation is only functional when the natural frequency of this oscillator is greater than a nominal frequency.
In conclusion, the teaching generally given to those skilled in the art is as follows: If it is sought to electronically regulate the frequency of a balance-hairspring of a conventional timepiece movement, it is necessary to change the balance-hairspring in order to firstly arrange at least one magnet on top and secondly to modify the natural frequency thereof such that this natural frequency is greater than the frequency sought. The consequence of such a teaching is obvious: It is necessary to misadjust the mechanical resonator so that it oscillates at an excessively high frequency so as to enable the regulation device to consistently return the frequency thereof to a lower frequency, corresponding to the theoretical frequency sought, by a succession of braking pulses. Consequently, the resulting timepiece movement is voluntarily set in such a way that precise operation is dependent on the electronic regulation, failing which such a timepiece movement would have a very significant time drift. As such, if for one reason or another the regulation device is deactivated, particularly due to damage, then the watch equipped with such a movement will no longer be precise, to an extent that it is actually no longer operational. Such a situation is problematic.
The use of a magnet-coil type electromagnetic system for coupling the balance-hairspring with the electronic regulation circuit gives rise to various problems. Firstly, the arrangement of permanent magnets on the balance results in a magnetic flux being consistently present in the timepiece movement and said magnetic flux varying spatially periodically. Such a magnetic flux may have a harmful effect on various members or elements of the timepiece movement, particularly on elements made of magnetic material such as parts made of ferromagnetic material. This may have repercussions on the proper operation of the timepiece movement and also increase wear of pivoted elements. It may indeed be envisaged to shield to a certain extent the magnetic system in question, but shielding requires specific elements which are borne by the balance. Such shielding tends to increase the size of the mechanical resonator and the weight thereof. Furthermore, it limits the possibilities of clean visually appealing configurations. Furthermore, a high-intensity external magnetic field may damage the magnetised elements of the electromagnetic system.
Those skilled in the art are aware of the proposed embodiments of mechanical timepiece movements, comprising a device for regulating the frequency of the balance-hairspring, where it is envisaged to act upon the oscillating balance with an electromechanical system formed, on one hand, by a stop which is arranged on the balance and, on the other, by an actuator equipped with a movable finger which is actuated at a defined braking frequency in the direction of the abutment. This concept is intended to synchronise the frequency of the oscillator against that of a quartz oscillator with a claimed interaction between the finger and the stop when the mechanical oscillator exhibits a time drift relative to the quartz oscillator, the finger either momentarily locking the balance which is then stopped in the movement thereof during a certain time interval (the stop bearing against the finger moved in the direction thereof upon the return of the balance towards the neutral position thereof), or limiting the oscillation amplitude when the finger arrives against the stop while the balance rotates in the direction of the maximum amplitude position thereof.
Such a regulation system has numerous drawbacks and it could seriously be doubted that it could form an operational system. The ‘blind’ action of the finger relative to the movement of the stop and to any potential initial phase shift of the oscillation of the stop in relation to that of the finger poses multiple problems. The action is limited to an angular position given by the position of the actuator relative to the balance-hairspring. As such, the effect of the interaction between the finger and the stop is dependent on the oscillation amplitude of the balance-hairspring and on the position of the actuator. In conclusion, such embodiments appear to a person skilled in the art to be highly unlikely, and such a person skilled in the art is deterred from such a use. Moreover, those skilled in the art of the present invention are not aware of watches equipped with such an electromechanical system that have been introduced onto the market.
An aim of the present invention is that of finding a solution to the technical problems and drawbacks mentioned above in the technological background.
A first aim, within the scope of the development leading to the present invention, was that of proposing a timepiece assembly comprising a mechanical movement, with a conventional balance-hairspring type mechanical resonator, and a regulating device which does not use a magnet-coil system for coupling the mechanical resonator to this regulating device, in particular which does not require arranging at least one permanent magnet on the balance. It shall be noted that, within the scope of the description of the present invention, such a magnet-coil system induces magnetic braking pulses, a magnetic flux generated by at least one coil being coupled with the magnetic flux of said at least one permanent magnet onboard the mechanical resonator.
A second aim, within the scope of the development resulting in the present invention, was that of producing a timepiece assembly comprising a mechanical movement with a mechanical oscillator and a device for regulating this mechanical oscillator, but without having to initially misadjust of the mechanical oscillator, in order to obtain a timepiece which has the precision of an auxiliary electronic oscillator (particularly equipped with a quartz resonator) when the regulating device is operational and the precision of the mechanical oscillator when this regulating device is deactivated or non-operational, but with a precision liable to correspond to the best standard in the latter case. In other words, it is sought to adjoin electronic regulation to a mechanical movement adjusted to the highest possible precision moreover such that it remains operational, with the best possible operation, when the electronic regulation is inactive.
The aim of the present invention is also that of proposing a timepiece assembly fulfilling at least the first aim and which is robust, i.e. which can retain a high precision even after an external disturbance such as a shock.
To this end, the present invention relates to a timepiece assembly as defined in claim 1, as well as to a regulating module as defined in claim 16. Diverse embodiments and variants are the subjet-matter of the dependent claims. Thus, the timepiece assembly according to the invention comprises an electronic control circuit, suitable for generating a control signal which is supplied to the regulation pulse application device for the activation thereof, and a sensor suitable for detecting the passage of the mechanical resonator via a certain given position on the oscillation axis. The regulating device of this timepiece assembly comprises a measuring device suitable for measuring, on the basis of position signals supplied by the sensor, a time drift of the mechanical oscillator relative to the auxiliary oscillator. Advantageously, the regulation pulse application device of the timepiece assembly is an electromechanical device suitable for generating, in response to the control signal mentioned above which is dependent on the time drift measured, mechanical braking pulses applied to the mechanical resonator, each applying a certain force couple to this mechanical resonator, to regulate the medium frequency of the mechanical oscillator, when at least a certain time drift of this mechanical oscillator is detected. Finally, the mechanical resonator defines a braking surface having a certain extent along the oscillation axis of the mechanical resonator and arranged in such a way as to enable at least the application of a mechanical braking pulse with the triggering thereof at a certain given time during an alternation, of the two alternations of an oscillation of the mechanical oscillator, regardless of the oscillation amplitude of this mechanical oscillator in an amplitude range having a certain extent and corresponding to a usable operating range of the mechanical oscillator, said given time being selected such that the passage via the neutral position of the mechanical resonator does not occur during the mechanical braking pulse.
The term ‘mechanical braking pulse’ denotes braking of mechanical nature and not merely a mechanical effect resulting from the braking. As such, this expression excludes in the first meaning assigned thereto contactless braking via an electromagnetic coupling between a stationary coil and at least one magnet mounted on the mechanical resonator, because in the latter case, the braking is magnetic and performed via an electromagnetic system wherein an element, i.e. said at least one magnet, is attached to an oscillating member of the mechanical resonator, thereby changing the conventional arrangement of the oscillating member, for example a balance. However, magnetic braking has the end result of reducing the mechanical energy of the oscillating member, but the braking is not mechanical in nature. The expression mentioned above also excludes braking resulting from electrical coupling between the oscillating member and a stationary unit of the regulating device. On the other hand, obviously, this expression does not exclude electrical and/or magnetic elements incorporated in the electromagnetic device which induces mechanical braking pulses applied to the mechanical resonator. On the other hand, the term ‘electromechanical’ indicates that at least one electrical element forms the regulation pulse application device.
In one preferred embodiment, the regulation pulse application device is formed by an actuator comprising at least one braking member suitable for being actuated, in response to the control signal mentioned above, so as to apply to the oscillating member of the mechanical resonator a certain mechanical force couple during the mechanical braking pulses. Braking is therefore obtained by physical contact between the braking member and the oscillating member.
In one advantageous alternative embodiment of the preferred embodiment mentioned above, the regulation pulse application device is arranged such that the braking energy of each mechanical braking pulse is less than a locking energy, so as not to stop the mechanical resonator momentarily during the braking pulses. Subsequently, the oscillating member and the braking member are arranged such that the mechanical braking pulses can be applied essentially by dynamic dry friction between the braking member and the braking surface of the oscillating member.
By means of the features of the invention, it is possible to adjoin to a basic mechanical movement a module for regulating the mechanical oscillator thereof (comprising a balance-hairspring) without having to modify this basic mechanical movement. This is a great advantage. In particular, the timepiece assembly according to the invention may be produced without having to vary the kinematic properties of the mechanical oscillator. If required, a surface treatment (generally partial) of the balance may be envisaged for the operation of the sensor. Such a treatment may be limited to affixing a black dot on one of the balance or under the felloe of said balance in the case of an optical sensor. As such, the design of the basic mechanical movement does not need to be changed to produce a timepiece assembly according to the invention. In a first case where the timepiece assembly is produced entirely as new, it is therefore possible to take an existing template having proven its worth in production and associate therewith an additional regulation module according to the invention, by arranging at the periphery of the timepiece movement corresponding to this template the regulating module so as to enable the application of the mechanical braking pulses to the mechanical resonator. At the exterior of the timepiece assembly, it will optionally be necessary to envisage an adaptation to enable the incorporation of the additional regulating module. In a second case, the timepiece assembly according to the invention is formed by a basic timepiece movement placed, firstly, on the market in a watch and to which is added, secondly, a regulating module according to the invention in order to increase the precision thereof. An adaptation at the exterior of the watch may prove to be necessary, but is not necessarily obligatory. For example, machining at a casing ring may prove to be sufficient to enable the incorporation of the timepiece assembly in the case already in a user's possession, i.e. with an addition of a regulating module according to the invention, the subject matter of the appended claims.
According to one main embodiment, the measuring device is suitable for determining whether the time drift of the mechanical oscillator corresponds to at least one advance or to at least one delay. Subsequently, the control circuit and the regulation pulse application device are suitable for selectively applying to the mechanical resonator, when the time drift measured corresponds to a certain advance, a first mechanical braking pulse wherein at least a main part occurs between the initial time and the median time of an alternation (first half-alternation) and, when the time drift measured corresponds to a certain delay, a second mechanical braking pulse wherein at least a main part occurs between the median time and the end time of an alternation (second half-alternation). It shall be noted that each oscillation period of the mechanical oscillator defines a first alternation followed by a second alternation and each alternation has a passage of the mechanical resonator via the neutral position at said median time.
As such, in sum, the control circuit and the regulation pulse application device are suitable for selectively applying to the mechanical resonator, when the time drift measured corresponds to a certain advance, a mechanical braking pulse in a first half-alternation of the oscillation of the mechanical resonator and, when the time drift measured corresponds to a certain delay, a mechanical braking pulse in a second half-alternation.
In a main alternative embodiment, the regulating device comprises a device for determining time positions of the mechanical resonator which is suitable for determining, in an alternation of an oscillation of the mechanical resonator, a first time which occurs prior to the median time and after the initial time of this alternation and, also in an alternation of an oscillation of this mechanical resonator, a second time which occurs after the median time and prior to the end time of this alternation. Subsequently, the control circuit is suitable for selectively triggering a first mechanical braking pulse substantially at the first time and a second mechanical braking pulse substantially at the second time. Finally, the braking surface of the mechanical resonator comprises a first sector, along the oscillation axis thereof, for applying the first mechanical braking pulse starting substantially at the first time and a second sector, along the oscillation axis, for applying the second mechanical braking pulse starting substantially at the second time, regardless of the oscillation amplitude of the mechanical oscillator in the usable operating range thereof.
The invention will be described in more detail hereinafter using the appended drawings, given by way of examples that are in no way limiting, wherein:
In
The timepiece assembly 2 further comprises a device 6 for electronically regulating the frequency of the mechanical oscillator, this regulating device comprising an electronic regulation circuit 22 associated with an auxiliary oscillator formed by a quartz resonator 23. It should be noted that other types of auxiliary oscillators may be envisaged, particularly an oscillator integrated entirely in the regulation circuit. By definition, the auxiliary oscillator is more precise than the mechanical oscillator. The device 6 also comprises a sensor 24 for detecting at least one angular position of the balance when it oscillates and a device 26 for applying regulation pulses to the mechanical resonator 14. Finally, the timepiece assembly comprises a power source 28 associated with a device 26 for storing the electricity generated by the power source. The power source is for example formed by a photovoltaic cell or by a thermoelectric element, these examples being in no way limiting. In the case of a battery, the power source and the storage device form together one and the same component.
As a general rule, the regulating device 6 comprises in the regulation circuit thereof an electronic control circuit suitable for generating a control signal, which is supplied to the regulation pulse application device which is suitable for generating, in response to this control signal, successive regulation pulses each applying a certain force couple to the mechanical resonator. According to the invention, the sensor 24 is suitable for detecting the passage of at least one reference point of the balance 16 via a certain given position relative to a support of this mechanical resonator. Preferably, the sensor is suitable for detecting at least the passage of the mechanical resonator via the neutral position thereof. It should be noted that, in this preferred alternative embodiment, the sensor may be associated with the escapement pallet assembly so as to detect the switching of this pallet assembly during the oscillation maintenance pulses envisaged substantially when the resonator passes via the neutral position thereof.
The detection of the neutral point of the resonator makes it possible to generate a usable and stable time reference within the oscillations. Indeed, in the absence of disturbances (particularly induced by the braking pulses envisaged for regulation), the passage via the neutral point always occurs exactly at the midpoint of the alternations, independently of the oscillation amplitude. On the other hand, the detection of another angular position of the balance does not give a stable and clearly defined time reference, particularly relative to the events such as the passage of the balance-hairspring via the neutral position thereof and the start or end of the alternations, i.e. the times where the balance is at maximum amplitude and at zero angular velocity (corresponding to the inversion of the oscillation direction). Furthermore, as the angular velocity of the balance-hairspring is maximum upon the passage thereof via the neutral position thereof, the precision of this detection and as such that detection of the corresponding time are superior. The benefit of detecting the passage of the balance-hairspring via the neutral position thereof will be clearly understood hereinafter during the disclosure of the preferred regulation method given with reference to
As a general rule, the regulating device 6 also comprises a measuring device suitable for measuring, on the basis of position signals supplied by the sensor, a time drift of the mechanical oscillator relative to the auxiliary oscillator. It is understood that such a measurement is easy once a sensor capable of detecting the passage of the mechanical resonator via the neutral point thereof is provided. Such an event takes place every oscillation half-period of the mechanical oscillator. The measurement circuit will be described in more detail hereinafter.
The regulation pulse application device 26 is suitable for applying to the balance 16 mechanical braking pulses for regulating the frequency of the mechanical oscillator when a certain time drift of said mechanical oscillator is observed. In one particular alternative embodiment, the braking energy drawn from the mechanical resonator by any mechanical braking pulse is envisaged to be less than the locking energy of the mechanical oscillator, so as not to momentarily stop the oscillation movement of the mechanical resonator during the regulation pulses. The locking energy is usually defined as the kinetic energy of the mechanical resonator at the start of the braking pulse less the difference in potential energy of this mechanical resonator between the end and the start of the braking pulse in question, insofar as the mechanical oscillator does not receive maintenance energy during this braking pulse. Therefore, this particular alternative embodiment involves reducing, during the braking pulse, the angular velocity of the balance-hairspring without stopping same for more or less a long time. It should be noted that, in order to ensure the proper operation of the Swiss pallet assembly escapement of a standard timepiece oscillator, it is preferable for the braking pulses not to occur during switching of the pallet assembly, during which switching maintenance energy is supplied from the oscillator. As the switching of the pallet assembly generally occurs about the neutral position of the mechanical resonator, disruption with a braking pulse of the oscillation movement of the balance-hairspring upon the passage thereof via this neutral position will therefore be prevented.
According to a first embodiment represented in
In one advantageous alternative embodiment (not shown), the balance comprises a central shaft which defines, respectively which bears a part other than the felloe of the balance defining, at least over a certain angular sector, a circular braking surface. In this case, a braking member pad is arranged so as to apply a pressure against this circular braking surface during the application of the mechanical braking pulses.
A circular braking surface, for an oscillating member which is pivoted (balance), associated with at least one braking pad, borne by the braking device of the regulating device, forms a mechanical braking system which has decisive advantages. Indeed, by means of such a system, braking pulses may be applied to the mechanical resonator at any time of the oscillations, regardless of the oscillation amplitude of the balance. Subsequently, the correction induced by a braking pulse can be managed precisely, in particular by suitable selection of the duration thereof and by the braking force couple applied. It is also possible, by means of the position measurement made by the sensor, to determine the times during the alternations in order to apply the braking pulses. As such, at least the braking torque, the duration of the pulses and the respective times at which they are induced may be selected and vary according to the time drift of the mechanical oscillator. In particular, it is thereby possible to induce slight corrections for fine and precise regulation of the oscillation frequency.
It should be noted that the oscillation amplitude generally varies according to the degree of arming of the barrel (unless a specific device for producing a constant force is envisaged). As such, at a non-null given time before or after the passage of the resonator via the neutral position thereof in any alternation of the oscillation movement thereof, the angular position of the balance varies according to the oscillation amplitude. If it is chosen for example to give braking pulses to regulate the oscillation frequency always at a defined fixed time interval before or after the passage of the resonator via the neutral position thereof (see the preferred regulation principle disclosed hereinafter), the braking surface should then extend over a certain angular length so that the pad can in any case apply a braking force on the balance at various angular positions along this braking surface. As such, the mechanical resonator has a braking surface which extends over at least a certain angular sector having a certain angular length which is different to zero (i.e. an angular sector is considered to be non-localised), to enable the application of mechanical braking pulses at least at a certain given time in the oscillation periods of the mechanical oscillator, regardless of the oscillation amplitude of the mechanical resonator for usable operating range of the mechanical oscillator.
It should be noted that, according to the time interval mentioned above or according to a time slot chosen to apply braking pulses before or after the passage times of the mechanical resonator via the neutral position thereof in various alternations of the oscillation movement thereof, times which are detected by the sensor 34, it is simply necessary for two defined angular sectors of the balance to have or define respectively two circular surfaces for the braking member pad so that the braking pulses can be applied in a usable operating range of the mechanical oscillator, i.e. over a certain usable angular range for the amplitude of the oscillations thereof (for example between 200° and 300°). In general terms, it is envisaged that the braking surface of the mechanical resonator braking surface of the mechanical resonator comprises at least one first angular sector for the application, in alternations, of first mechanical braking pulses substantially at a first time situated before the median passage time of the mechanical resonator via the neutral position thereof and a second angular sector for the application, in alternations, of second mechanical braking pulses substantially at a second time situated after the median time, regardless of the oscillation amplitude of the mechanical resonator in a usable operating range of the mechanical oscillator in question. It should be noted that, in a specific case where the first time and the second time are envisaged in alternations at the same time distance from the median time and on the same side of the neutral position, the first and second angular sectors are substantially merged and thereby define one and the same angular braking sector. In other cases, the first and second angular sectors have a common part or are separate. The same considerations apply to a first time interval and a second time interval wherein it is possible to envisage respectively applying the first and second braking pulses. In the alternative embodiment represented in
It should further be noted that the braking member pad may also have a circular contact surface, of the same radius as the braking surface, but such a configuration is not required. The contact surface may particularly be planar, as shown in the figures. A planar surface has the advantage of allowing a certain margin in the positioning of the braking member relative to the balance, which makes it possible to have greater manufacturing and assembly tolerances of the braking device in the or at the periphery of the timepiece movement.
The sensor 34 is a photoelectric type optical sensor. It comprises a light source, suitable for sending a light beam towards the balance, and a light detector, suitable for receiving a light signal in return, the intensity whereof varies periodically according to the position of the balance. In the schematic example shown in
In other alternative embodiments, the position sensor may be of the capacitive type or of the inductive type and as such be suitable for detecting a variation in capacitance, or of inductance according to the position of the balance. The inductive sensor preferably functions without the presence of magnetised material on the resonator, for example by detecting the presence of non-magnetised material or merely a variation in distance between such a material and the sensor. Those skilled in the art know numerous sensors which could be readily incorporated in the timepiece assembly according to the invention.
Advantageously, the various elements of the regulating device 6 form an independent module of the timepiece movement. As such, this module may be assembled or associated with the mechanical movement 4 only during the assembly thereof particularly in a watch case. In particular, such a module may be attached to a casing ring surrounding the timepiece movement. It is understood that the electronic regulation module may therefore be advantageously associated with the timepiece movement once the latter is entirely assembled and adjusted, the assembly and disassembly of this module being possible without having to work on the mechanical movement per se.
A regulation method will be described hereinafter, with reference to
Each oscillation period of the mechanical oscillator defines a first alternation followed by a second alternation between two end positions defining the oscillation amplitude of this mechanical oscillator, each alternation having a passage of the mechanical resonator via the neutral position thereof at a median time tZn and a duration between an initial time tAn-1, respectively tD1 for the alternation A1 in
A variation in the oscillation period during which the braking pulse occurs and therefore an isolated variation of the frequency of the mechanical oscillator are observed. In fact, as seen in the last two graphs in
The term braking pulse denotes an application, substantially during a limited time interval, of a certain force couple to the mechanical resonator braking same, i.e. a force couple opposing the oscillation movement of this mechanical resonator. Within the scope of the invention, each braking pulse is generated by mechanical braking applying a mechanical braking couple to the mechanical resonator, as shown by the third graph representing the angular velocity of the balance.
In
The behaviour of the mechanical oscillator in a first correction scenario of the oscillation frequency thereof, corresponding to that shown in
In this first case, the braking pulse is generated between the start of an alternation and the passage of the resonator via the neutral position thereof in this alternation. As envisaged, the angular velocity in absolute values decreases during the braking pulse P1. Such a braking pulse induces a negative time phase shift TC1 in the oscillation of the resonator, as shown by the two graphs of the angular velocity and of the angular position in
With reference to
In the second case in question, the braking pulse is therefore generated, in an alternation, between the median time at which the resonator passes via the neutral position thereof and the end time at which this alternation ends and at which the resonator occupies an end position. As envisaged, the angular velocity in absolute values decreases during the braking pulse P2. Remarkably, the braking pulse induces herein a positive time phase shift TC2 in the oscillation of the resonator, as shown by the two graphs of the angular velocity and the angular position in
This regulation method is remarkable in that it makes use of a surprising physical phenomenon of the mechanical oscillator. The inventors arrived at the following observation: Unlike the general teaching in the field of timepieces, it is possible not only to reduce the frequency of a mechanical oscillator with braking pulses, but it is also possible to increase the frequency of such a mechanical oscillator also with braking pulses. Those skilled in the art would expect to be able to practically only reduce the frequency of a mechanical oscillator with braking pulses and, by way of corollary, to be able to only increase the frequency of such a mechanical oscillator by applying drive pulses when supplying power to said oscillator. Such an intuitive idea, which has become established in the field of timepieces and therefore comes first to the mind of those skilled in the art, proves to be incorrect for a mechanical oscillator. Although such behaviour is correct for a micro-generator, wherein the rotor rotates continuously in the same direction, this is on the contrary not true for a mechanical oscillator in that it oscillates.
Indeed, it is possible to regulate electronically, via an auxiliary oscillator comprising for example a quartz resonator, a mechanical oscillator that is moreover high-precision, so that it momentarily exhibits a frequency that is slightly too high or too low. To do this, it is envisaged to select correctly, according to the operating of the mechanism in question and therefore the frequency of the mechanical oscillator setting the pace of this operation, the time to apply a mechanical braking pulse. The inventors observed that the effect produced by a regulation pulse on a mechanical resonator is dependent on the time when it is applied in an alternation relative to the time when this mechanical resonator passes via the neutral position thereof. According to this principle revealed by the inventors and used in a timepiece assembly according to the invention, a braking pulse applied, in any alternation between the two end positions of the mechanical resonator, substantially prior to the passage of the mechanical resonator via the neutral position thereof (idle position) produces a negative time phase shift in the oscillation of said resonator and therefore a delay in the operation of the mechanism paced by the resonator, whereas a braking pulse applied in this alternation substantially after the passage of the mechanical resonator via the neutral position thereof produces a positive time phase shift in the oscillation of said resonator and thereof an advance in the operation of the mechanism. It is thereby possible to correct a frequency that is too high or a frequency that is too low merely by means of braking pulses. In sum, applying a braking couple during an alternation of the oscillation of a balance-hairspring induces a negative or positive phase shift in the oscillation of said balance-hairspring according to whether said braking torque is applied respectively before or after the passage of the balance-hairspring via the neutral position thereof.
Making use of the physical phenomena described above, a main embodiment of the timepiece assembly according to the invention is characterised by a particular arrangement of the regulating device of the mechanical oscillator and particularly the electronic regulation circuit. Generally, this regulation device comprises a measuring device suitable for measuring, if applicable, a time drift of the mechanical oscillator relative to an auxiliary oscillator, which is implicitly more precise than the mechanical resonator, and for determining whether this time drift corresponds to at least a certain advance or to at least a certain delay. Then, the regulating device comprises a control circuit connected to the regulation pulse application device described above, which are suitable for applying to the mechanical resonator, when the time drift of the mechanical oscillator corresponds to at least a certain advance, a first braking pulse substantially in a first half-alternation prior to the median passage time of the mechanical resonator via the neutral position thereof and, when the time drift of the mechanical oscillator corresponds to at least a certain delay, a second braking pulse substantially in a second half-alternation after the median passage time of the mechanical resonator via the neutral position thereof.
In one preferred embodiment that will be described in more detail hereinafter, the regulating device comprises a device for determining time positions of the mechanical resonator, this determining device being suitable for determining, in an alternation of an oscillation, a first time occurring prior to the median passage time of the mechanical resonator via the neutral position thereof and after the initial time at which this alternation starts, as well as, in the same alternation or another alternation of an oscillation, a second time occurring after the median passage time of the mechanical resonator via the neutral position thereof and before the end time at which this alternation ends. Subsequently, the control circuit is suitable for selectively detecting a first braking pulse substantially at the first time and a second braking pulse substantially at the second time.
It should be noted that the device for determining time positions of the mechanical resonator may have elements or members in common with the measuring device, in particular the position measurement sensor, and with the control circuit, for example a logic circuit and operationally a counter. However, such embodiments are in no way limiting within the scope of the present invention.
With reference to
The comparator is an element of a measurement circuit 52 described hereinafter. Given that there are two pulses 42 per oscillation period of the mechanical resonator, the digital signal ‘Comp’ is supplied to a lever 54, which regularly supplies one pulse per oscillation period. The lever increments, at the instantaneous frequency of the mechanical oscillator, a bidirectional counter C2, which is decremented at a nominal frequency/set-point frequency by a clock signal Shor derived from the auxiliary oscillator which generates a digital signal at a reference frequency. This auxiliary oscillator is formed from the auxiliary resonator 23 and a clock circuit 56. For this purpose, the relatively high-frequency reference signal generated by the clock circuit is previously split by the splitters DIV1 and DIV2 (these two splitters optionally forming two stages of the same splitter). As such, the state of the counter C2 determines the advance or delay accumulated over time by the mechanical oscillator relative to the auxiliary oscillator with a resolution corresponding substantially to the set-point period, the state of the counter being supplied to a logic control circuit 58. The state of the counter C2 corresponds to the time drift of the mechanical oscillator.
As indicated in the flow chart in
If the condition C2>N1 is verified (‘true’), then the control circuit waits until the counter C1 has measured a first time interval TA1 (see
If the condition C2<-N2 is verified (‘true’), then the control circuit waits until the counter C1 has measured a second time interval TA2 (see
It should be noted that, in
It should be noted that, in the case where C2>N1 or C2<-N2, it can be envisaged, in one alternative embodiment, to supply a plurality of successive control pulses at a plurality of times tZn+TA1, respectively tZn+TA2 according to the method described. This involves inhibiting the query of the state of the counter C2 during a certain number of sequences. Such an alternative embodiment makes it possible to supply a succession of low-energy braking pulses. In order to limit the possible range for the time drift of the oscillator, low values will preferably be taken for N1 and N2. For example N1=N2=1 or 2.
The sensor, the comparator 50, the control circuit 58 and the counter C1, incremented by the clock circuit 60 via the splitter DIV1, form together a device for determining time positions of the mechanical resonator which makes it possible to apply mechanical braking pulses in various alternations selectively before and after the passage of the mechanical resonator via the neutral position thereof. As such, the preferred regulation method described above may be implemented effectively and safely, so as to correct a natural frequency of the mechanical oscillator which is too high or too low relative to the set-point frequency generated by the clock circuit 60 via the splitters. The device for determining time positions is therefore suitable for measuring, following the detection of a passage of the resonator via the neutral position thereof, a first time interval and a second time interval wherein the respective ends define respectively a first time and a second time which are situated temporally, in any alternation of the oscillation of the mechanical resonator, respectively before and after the time of the passage of said resonator via the neutral position thereof.
With reference to
It is envisaged, in the present alternative embodiment, to set the sensor to the ‘OFF’ state during the main part of each oscillation of the mechanical oscillator. For this purpose, the control circuit 58A is suitable for supplying a control signal SCAP to a switch 68 which controls the power supply of the sensor 24, respectively which controls the state of said sensor between the ‘ON’ state thereof and the ‘OFF’ state thereof. As indicated by the signals SCAP and Comp in
In the flow chart in
During the activation of the regulating device, the sensor is set directly to the ‘ON’ state thereof pending the detection of the falling edge of a first pulse 42 (corresponding to a passage via the neutral position of the mechanical resonator). Once this detection has taken place, the sensor is set to the ‘OFF’ state thereof (sensor OFF) and the regulation sequence continues as in the preceding alternative embodiment. On the other hand, whether a braking pulse is generated or not, the control circuit 58A continues to follow the incrementation of the counter C1 until the value thereof corresponds to the time interval TOFF envisaged. Then the sequence ends with a further activation of the sensor (Sensor ON) which also marks the start of a subsequent sequence. The algorithm as given in
With reference to
In one alternative embodiment, the braking force applied to the balance may be envisaged to be axial. In such an alternative embodiment, it is advantageous to envisage a braking device of the type proposed in
An actuator forming a particular braking device is shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 16206778.9 | Dec 2016 | EP | regional |
| 17172554.2 | May 2017 | EP | regional |
