HK1185157B - Circuit for autoregulating the oscillation frequency of an oscillating mechanical system and device including the same - Google Patents

Description

Circuit for automatically adjusting the oscillation frequency of an oscillating mechanical system and device comprising such a circuit

Technical Field

The invention relates to a circuit for automatically adjusting the oscillation frequency of an oscillating mechanical system.

The invention also relates to a device comprising an oscillating mechanical system and a circuit for automatically adjusting the oscillation frequency of the oscillating mechanical system.

Background

In the field of horology, the oscillating mechanical system may be a balance on which a balance spring is mounted, one end of which is fixed to the rotating balance staff and the other end of which is fixed to a fixed element of the chassis. The oscillation of the mechanical system is maintained via an energy source that is typically mechanical. This energy source may be, for example, a barrel driving a gear train with an escape wheel cooperating with a pallet lever. For example, this rotary pawl lever actuates a pin fixed near the rotary pendulum shaft. The balance with the balance spring may thus form a regulating component of a timepiece movement. This oscillation regulating member determines the driving speed of the gear train, wherein the escape wheel leads to the time hand.

In order to adjust precisely the oscillation frequency of the oscillating mechanical system, it is possible to adapt the length of the balance spring, either adding weight to or removing weight from the outer circular portion of the balance. In the case of a watch, however, all these additional adjustment elements take up considerable space within the watch case and lead to relatively long manufacturing times and high costs. This constitutes a drawback.

In mechanical or electromechanical watches, it is known to regulate the rotational speed of a generator connected to a spiral spring barrel to mechanically drive the hands of the watch via a gear train. The generator generates an alternating voltage which is rectified by a rectifier of the electronic regulating circuit. The function of this regulating circuit is to control the rotational speed of the generator so that the time hands can be moved in accordance with the correct current time indication. The transistors of the regulating circuit may short-circuit the generator for a determined period of time to brake the generator and thereby regulate the rotational speed. In this respect, reference may be made to EP patent applications 0762243a1 or 0822470a1, which disclose watches equipped with a regulating circuit of this type.

The above mentioned generator comprises a rotating permanent magnet and a coil opposite the magnet, so that an induced alternating voltage can be provided. Manufacturing this type of generator and regulating circuit can be complicated. Designing the generator with the regulating circuit usually requires the provision of a large number of components. Furthermore, the magnetic field of the rotating magnet may cause interference with certain nearby ferromagnetic parts. This constitutes a number of drawbacks.

Instead of a generator formed by a rotating permanent magnet and a coil generating an induced alternating voltage, FR patent 2119482 has proposed providing an oscillating mechanical system with a piezoelectric element. This piezoelectric element is preferably arranged on a balance spring connected to the balance. To achieve this, a thin film of piezoelectric material (PZT) is deposited over a substantial length of the spring, as well as on the inner and outer surfaces of the metal spring. The voltage converter supplies an alternating voltage to the piezoelectric element to alternately generate a compression force and an expansion force on the balance spring, so as to regulate the oscillation of the balance wheel connected to the balance spring. However, in this patent document, there is no mention of using an automatic adjustment circuit to adjust the oscillation frequency of a balance with a hairspring, which is a disadvantage.

From JP patent application 2002-. The alternating voltage is rectified in a rectifier comprising at least two diodes and FET transistors controlled by an electronic regulating circuit. The rectified voltage is stored at least in a supply voltage storage capacitor. The electronic circuit may be directly supplied with power by an alternating voltage from a generator, which alternating voltage has been rectified and stored in a capacitor. The piezoelectric generator is of the bimetal type (PZT). To adjust the oscillation frequency, a signal having a reference frequency provided by a quartz oscillator circuit is compared with an alternating signal from the generator. With the proposed electronic circuit, it is not possible to design a very compact oscillating mechanical system with a regulating circuit in an easily realizable manner, which constitutes a drawback.

Disclosure of Invention

It is therefore an object of the present invention to provide a compact automatic adjustment circuit with a limited number of components to accurately adjust the oscillation frequency of an oscillating mechanical system and to overcome the above-mentioned drawbacks of the prior art.

The invention therefore relates to a circuit for automatically adjusting the oscillation frequency of an oscillating mechanical system comprising the features mentioned in independent claim 1.

Particular embodiments of the automatic regulating circuit are defined in the dependent claims 2-10.

One advantage of this autoregulating circuit according to the invention is that it can be manufactured in the form of a single electronic module that can be connected, directly or via two wires, to a piezoelectric element or an electroactive polymer element provided on the oscillating mechanical system. This oscillating mechanical system may preferably be a balance on which a balance spring is arranged, the balance spring comprising a piezoelectric or electroactive polymer element.

Advantageously, the autoregulating circuit comprises an oscillator stage connected to a MEMS resonator that can be placed or manufactured on, beside or in the same substrate on which the other components of the autoregulating circuit are integrated. In this way, the autoregulating circuit with all these components forms a single compact component. This significantly reduces the dimensions of the oscillating mechanical system with the automatic oscillation frequency adjustment circuit, which can therefore be advantageously installed in a mechanical watch.

Advantageously, the autoregulating circuit is able to apply an adaptive voltage on the piezoelectric or electroactive polymer element to generate a compression or expansion force continuously or at determined time periods. This allows adjustment of the oscillation frequency of the oscillating mechanical system. For this purpose, a comparison is made between the frequency of the reference signal generated via the oscillator stage and the frequency of the alternating voltage generated by the piezoelectric element or electroactive polymer element.

The invention therefore also relates to a device comprising said oscillating mechanical system and said circuit for automatically adjusting the oscillation frequency of the oscillating mechanical system, which device comprises the features mentioned in independent claim 11.

Particular embodiments of the device are defined in the dependent claims 12-15.

Drawings

The objects, advantages and features of the oscillating frequency automatic adjustment circuit of an oscillating mechanical system and of the device comprising such a circuit will become clearer in the following description, made with reference to at least one non-limiting embodiment illustrated in the attached drawings, wherein,

figure 1 shows a simplified diagram of a device comprising an oscillating mechanical system and an automatic oscillation frequency adjustment circuit for an oscillating mechanical system according to the invention,

figure 2 shows a part of a balance spring of an oscillating mechanical system comprising a piezoelectric or electroactive polymer element of a device according to the invention, and

fig. 3 shows a simplified block diagram of the electronic components of the autoregulating circuit connected to the piezoelectric element or electroactive polymer element of the oscillating mechanical system according to the invention.

Detailed Description

In the following description, all electronic components familiar to those skilled in the art of the oscillation frequency automatic adjustment circuit of an oscillating mechanical system are described only in a simplified manner. As described below, the autoregulating circuit is mainly used to regulate the oscillation frequency of a balance wheel on which a balance spring with a piezoelectric or electroactive polymer element is mounted. However, other oscillating mechanical systems may also be considered, for example an acoustic system such as a tuning fork, but in the following description reference will be made only to an oscillating mechanical system in the form of a balance with a balance spring comprising a piezoelectric element or an electroactive polymer (EAP) element.

Fig. 1 shows a device 1 comprising an oscillating mechanical system 2, 3 and a circuit 10 for automatically adjusting the oscillation frequency fosc of the oscillating mechanical system. In a mechanical watch, the oscillating mechanical system may comprise a balance 2 formed by a metal ring, for example connected to a rotating shaft 6 by 3 arms 5, and a balance spring 3 on which a piezoelectric element or an electroactive polymer element is arranged, as will be explained briefly below. Balance pin 4 of the balance bar (not shown in the figures) firmly holds first end 3a of balance spring 3. The wobble pin is secured to the chassis (not shown) of the watch movement. The second end 3b of balance spring 3 is fixed directly to rotary balance staff 6.

The oscillation of balance 2 with hairspring 3 is maintained via an energy source (not shown in the figures), which may be electric, but is preferably mechanical. This mechanical energy source may be a barrel, which conventionally drives a gear train with an escape wheel cooperating with a pallet lever. For example, this rotary pawl lever actuates a pin fixed near the rotary pendulum shaft. The balance with the balance spring may thus form a regulating component of a timepiece movement.

As shown in part in figure 2, balance spring 3 is made, in a known manner, using a wire or strip which is generally less than 0.3mm (for example, about 0.025-0.045 mm) thick. At least one piezoelectric or electroactive polymer layer 23 is deposited on one of the surfaces of the metal strip 24 before the metal strip 24 is wound in a spiral shape, preferably hot, using mutually spaced coils. For example, this piezoelectric layer may be formed of titanium oxide, preferably less than 0.1mm thick.

It is also possible to deposit a first piezoelectric or electroactive polymer layer 23 on one face, designated the outer face, and a second piezoelectric or electroactive polymer layer 23' on the other face, designated the inner face. When winding a metal strip with a piezoelectric or electroactive polymer layer 23, 23', the inner surface is the surface opposite the rotary pendulum shaft, while the outer surface is opposite the inner surface.

Preferably, the piezoelectric or electroactive polymer layers 23, 23' are deposited along the entire length of the metal strip 24, but it is also contemplated that only a portion of the metal strip may be coated with one or several piezoelectric or electroactive polymer layers. It is also contemplated to manufacture the metal strips entirely from piezoelectric material or electroactive polymer material, for example having a circular or rectangular cross-section.

When balance 2 oscillates with balance spring 3, a compression or expansion force is alternately applied to the piezoelectric or electroactive polymer layer, generating an alternating voltage. The oscillation frequency of balance 2 with balance spring 3 may be between 3 and 10 Hz. Thus, autoregulating circuit 10 is electrically connected to both piezoelectric or electroactive polymer layers to receive this alternating voltage. The autoregulating circuit can be connected to both ends of the piezoelectric or electroactive polymer layer, either directly or via two wires.

Fig. 3 shows various electronic components of the automatic adjusting circuit 10 for adjusting the oscillation frequency of the oscillating mechanical system. The autoregulating circuit 10 is connected to both ends of a piezoelectric or electroactive polymer element 23 placed on the balance spring of an oscillating mechanical system, such as a balance. The autoregulating circuit 10 is able to couple, via a conventional rectifier 11, an alternating voltage V received from a piezoelectric or electroactive polymer element 23_PRectification is performed. Alternating voltage V_PIs stored in the capacitor Cc. End V of capacitor Cc_DDAnd V_SSThis rectified voltage in between is sufficient to power all the electronic components of the autoregulating circuit without using an additional voltage source such as a battery.

The autoregulating circuit 10 includes an oscillator stage 15 connected to a MEMS resonator 16. The oscillator stage and the oscillating circuit of the MEMS resonator provide an oscillating signal, which may have a frequency below 500kHz, for example about 200 kHz. Thus, the preferred oscillator stage 15 may provide the reference signal V_RReference signal V_RMay be equal to the frequency of the oscillating signal from the oscillator circuit.

It is also conceivable to include at least one oscillator stage of a frequency divider for dividing the frequency of the oscillating signal, in order to provide the reference signal V at a frequency divided with respect to the frequency of the oscillating signal_R. In such a case, the reference signal V_RMay be at a frequency V corresponding to the alternating voltage generated by the piezoelectric or electroactive polymer element_POf the same order of magnitude.

The MEMS resonator can be fabricated in a thick, SOI-type monolithic silicon substrate. All other components of the autoregulating circuit 10 can also be integrated using the same substrate. To achieve this, another thin SOI layer may be deposited on the thick SOI substrate to integrate other electronic components. Thus, the autoregulating circuit can form a single compact electronic module for regulating the oscillation frequency of the oscillating mechanical system. The self-regulating circuit manufactured may also be encapsulated in an opaque plastic material in a conventional manner. This reduces the interconnections to other external components and also reduces the consumption of electrical energy.

It should be noted that it is also contemplated to fabricate the MEMS resonator in the first monolithic silicon substrate. The MEMS resonator may be placed on or next to a second silicon monolithic substrate that integrates the other components of the autoregulating circuit. The two substrates are encapsulated in a conventional opaque plastic material to form a single compact module.

In order to be able to adjust the oscillation frequency of an oscillating mechanical system, it is necessary to apply an alternating voltage V in the automatic adjustment circuit 10_PAnd a reference signal V_RA comparison is made between. To achieve this, the autoregulating circuit 10 includes a device for applying an alternating voltage V_PFrequency of and reference signal V_RAnd comparison means 12, 13, 14, 17 for comparing the frequencies of (a) and (b). If the reference signal frequency matches the frequency of the oscillating signal from the oscillator stage 15, i.e. a frequency in the order of 200kHz, the comparison means must be designed to take into account the alternating voltage V_PAnd a reference signal V_RWith a considerable frequency gap in between.

First, fromA first alternating counter 12 forms the comparison device, the first alternating counter 12 receiving an alternating voltage V at the input from a piezoelectric or electroactive polymer element_PAnd provides the processor unit 17 with a first count signal N_P. The comparison device further comprises a second alternation counter 14, the second alternation counter 14 receiving the reference signal V at an input_RAnd provides a second count signal N to the processor unit 17_R。

To take into account the alternating voltage V_PAnd a reference signal V_RWith a frequency gap in between, a measurement window 13 is provided between the first alternation counter 12 and the second alternation counter 14. The measurement window 13 determines the count time of the second alternation counter 14. The processor unit 17 provides configuration parameters to the measurement window 13 to determine the count time of the second alternation counter. These configuration parameters are stored in a memory (not shown in the figure) in the processor unit. These configuration parameters may vary depending on whether a female or male form is used. The various operations processed in the processor unit 17 may be controlled by a clock signal provided by an oscillator circuit, e.g. of the oscillator stage 15.

The count time of the second alternation counter 14 is proportionally adapted to the first count signal N_POf a certain number of alternations counted by the first alternation counter. The processor unit may also control the first alternation counter 12 to define the start and the end of a counting period. It is also conceivable to let the first alternation counter 12 provide information to the processor unit about the beginning and the end of the counted determined number of alternations. For example, if 200 alternations are counted in the first alternation counter, the measurement window 13 is configured such that the second alternation counter 14 is aligned to the reference signal V during a time period which is one-half 5000 of the time period_RThe number of alternations of (a) is counted. This time period may also depend on the count time, e.g. on 200 alternations of the first alternation counter. This reduces the power consumption of the autoregulating circuit.

The start of the counting controlled by the measurement window 13 may be controlled by the firstThe alternation counter 12 determines, but may preferably also be controlled directly by the processor unit 17. First, the processor unit may receive an alternating voltage V for a first time period_PIs determined by a first count signal N related to the counted first determined number of alternations_P. For example, the first count signal is stored in a register of the processor unit. Next, the processor unit may receive a second count signal N related to a second number of alternations counted in a second alternation counter 14 in a second time period controlled by the measurement window 13_R. This second count signal N may also be used_RIn another register of the processor unit. Finally, the two count signals are compared in the processor unit to determine the alternating voltage V_PIs proportionally too high or too low with respect to the reference signal frequency.

Based on counting two signals N in the processor unit_PAnd N_RThe processor unit operates a frequency adaptation unit 18, the output of the frequency adaptation unit 18 being connected to the end of a piezoelectric or electroactive polymer element 23. This frequency adaptation unit 18 may be arranged to provide a frequency adaptation signal being a continuous voltage V_AThe level of which is a function of the difference between the two count signals delivered by the processor unit. For this purpose, a switchable capacitor or resistor array may be provided. The voltage follower of the adaptation unit 18 may provide a continuous voltage value to one end of the piezoelectric or electroactive polymer element 23 or to the other end of the piezoelectric or electroactive polymer element. This therefore induces on the piezoelectric or electroactive polymer element a certain force that brakes or accelerates the oscillation of the oscillating mechanical system, depending on the comparison of the two counting signals.

The frequency adaptation unit 18 may provide the signal with a certain value V at certain time periods_ACan be programmed in the processor unit. In order to save energy, it is also possible to arrange for the electronic components of the autoregulating circuit to be switched on only for a certain period of time. E.g. measurement window 13, second alternating countThe device 14, the oscillator stage 15 connected to the MEMS resonator 16 and a part of the processor unit 17 may be left in a rest state and switched on for a determined period of time to adjust the oscillation frequency. However, the first alternation counter 12, which operates at a very low frequency, may be switched on continuously and may be at an alternating voltage V_PIs used to control the switching on of the other parts of the autoregulating circuit 10 after a certain counted number of alternations.

The non-engagement time, in particular of the oscillator stage 15, can be extended if the oscillation frequency of the oscillating mechanical system has been adapted. Under these conditions, for example, most of the idle electronic components of the autoregulating circuit can be switched on every minute, which greatly reduces the power consumption of the autoregulating circuit. Under these conditions, the capacitor Cc storing the rectified supply voltage is hardly unloaded, since it is only when at the reference signal V_RAnd an alternating signal V_PThe frequency comparison between them is made, and then the larger energy is used by chance.

The autoregulating circuit 10 may also include known thermal compensation elements and a reset unit for each time the autoregulating circuit 10 is turned on. All electronic components of the autoregulating circuit, the MEMS resonator 16 and the capacitor Cc form part of the same compact electronic module. All these electronic components are advantageously integrated in the same monolithic silicon substrate, which means that only one self-powered electronic module is required for adjusting the oscillation frequency of the oscillating mechanical system.

If the oscillator stage 15 is pressed against the alternating voltage V of the piezoelectric or electroactive polymer element 23_PIs matched with the desired frequency to provide a reference signal V_RThe first alternation counter 12 can directly control the counting time of the second alternation counter 14. The alternating voltage V may be applied in the processor unit 17_PNumber of alternations N_PWith the number of alternations N counted in the second alternation counter 14_RThe comparison was performed directly.

From the description made above, it is clear that a person skilled in the art can devise several variants of a circuit for automatically adjusting the oscillation frequency of an oscillating mechanical system and of a device comprising said circuit, without departing from the scope of the invention as defined by the claims. The oscillating mechanical system may be an acoustic system. The oscillation frequency of the oscillating mechanical system can be adapted by placing a number of capacitors in parallel with the piezoelectric or electroactive polymer element based on a frequency comparison between the alternating voltage and the reference signal. It is contemplated that a composite metal ion layer may be deposited on the balance spring for the same purpose as the piezoelectric element.

Claims (15)

1. A circuit (10) for automatically adjusting the oscillation frequency of an oscillating mechanical system (2, 3), wherein the mechanical system comprises an alternating voltage (V) capable of generating oscillations following the mechanical system_P) Is intended to be connected to a piezoelectric or electroactive polymer element (23) to adapt the oscillation frequency of an oscillating mechanical system, and said circuit (10) comprises:

-a rectifier (11) for the alternating voltage (V) generated by the piezoelectric or electroactive polymer element_P) Into-line rectification and for storing the rectified voltage in at least one capacitor (Cc) for supplying said circuit (10),

-an oscillator stage (15) comprising an oscillating circuit connected to the MEMS resonator (16) to provide a reference signal (V)_R），

-comparison means for comparing the alternating voltages (V)_P) Frequency of (d) and reference signal (V)_R) The frequency of (a) of (b) is,

-a frequency adaptation unit (18) intended to be connected to the piezoelectric or electroactive polymer element (23) to provide a frequency adaptation signal (V) to the piezoelectric or electroactive polymer element based on the comparison result in the comparing means_A) To adjust the oscillation frequency of the oscillating mechanical system, and

-all electronic components of the circuit (10) are grouped together to form a single electronic module,

characterised in that the comparison means comprise a first alternation counter (12) for alternating voltage (V) to the piezoelectric or electroactive polymer element during a first determined time period_P) And for providing a first count signal (N)_P) (ii) a A second alternation counter (14) for providing a reference signal (V) to the oscillator stage (15) during a second determined time period based in part on the first determined time period_R) And for providing a second count signal (N)_R) (ii) a And a processor unit (17) for comparing the first count signal with the second count signal to control the frequency adaptation unit (18) based on the comparison result.

2. Circuit (10) according to claim 1, characterized in that the MEMS resonator is manufactured in a monolithic silicon substrate also used for integrating all other electronic components of the circuit (10) to form a single compact module.

3. Circuit (10) according to claim 1, characterized in that the MEMS resonator is manufactured in a first monolithic silicon substrate placed on or beside a second monolithic silicon substrate for integrating other components of the circuit (10), both substrates being packaged to form a single compact module.

4. A circuit (10) as claimed in claim 1, characterized in that the oscillator stage (15) is adapted to provide a reference signal (V) having the same frequency as the frequency of the oscillating signal from the oscillating circuit_R）。

5. A circuit (10) as claimed in claim 4, characterized in that the oscillator stage (15) is configured to provide a reference signal (V) having a frequency higher than or equal to 200kHz_R）。

6. A circuit (10) as claimed in claim 1, characterized in that the comparison means further comprise a measurement window (13) arranged between the first alternation counter (12) and the second alternation counter (14), wherein the measurement window (13) is configured, while taking into account the first time period, using configuration parameters provided by the processor unit (17) to determine a second counting time period of the second alternation counter (14).

7. A circuit (10) as claimed in claim 1, characterized in that the oscillator stage (15) comprises a frequency divider for dividing the frequency of the oscillating signal to provide the reference signal (V)_R) Said reference signal (V)_R) According to the alternating voltage (V) of a piezoelectric or electroactive polymer element_P) Is defined and the processor unit (17) controls the counting operation of the first and second alternation counters (12, 14), wherein the first counting period is the same as the second counting period.

8. A circuit (10) as claimed in claim 1, characterized in that the frequency adaptation unit (18) is adapted to supply a continuous adaptive voltage to the piezo-electric or electroactive polymer element (23) on the basis of the comparison result in the processor unit (17) of the comparing device.

9. The circuit (10) according to claim 8, characterized in that the frequency adaptation unit (18) is adapted to provide a continuous adaptive voltage during a determined time period.

10. A circuit (10) as claimed in claim 1, characterized in that the first alternation counter (12) is adapted to switch on the oscillator stage (15), the second alternation counter (14) and a part of the processor unit (17) with a determined period for the frequency comparison, and that outside said determined period the rectified voltage in the capacitor (Cc) does not supply the oscillator stage (15), the second alternation counter (14) and a part of the processor unit (17).

11. A device comprising an oscillating mechanical system (2, 3) and an electric circuit (10) for automatically adjusting the oscillation frequency of the oscillating mechanical system according to claim 1, characterized in that the oscillating mechanical system (2, 3) comprises a piezoelectric or electroactive polymer element (23) for generating an alternating voltage at a frequency matching the oscillation frequency of the oscillating mechanical system, said piezoelectric or electroactive polymer element being connected at both ends to the electric circuit (10) so as to be based on the alternating voltage (V)_P) And a reference signal (V) from an oscillator stage (15) of the circuit (10)_R) Receives a frequency adaptation signal (V) from the circuit (10)_A）。

12. Device according to claim 11, characterized in that the oscillating mechanical system (2, 3) is a balance (2) of a watch in which a balance spring (3) is mounted, said spring carrying a piezoelectric or electroactive polymer element (23).

13. A device according to claim 12, characterised in that the piezoelectric or electroactive polymer element (23) comprises at least one layer of piezoelectric or electroactive polymer arranged on at least one surface of the metal strip (24) of the balance spring (3).

14. A device according to claim 13, characterized in that the piezoelectric or electroactive polymer element comprises a first piezoelectric or electroactive polymer layer arranged on the outer surface of the metal strip (24) and a second piezoelectric or electroactive polymer layer arranged on the inner surface of the metal strip (24), the first connection end of the piezoelectric or electroactive polymer element being fixed to the first piezoelectric or electroactive polymer layer and the second connection end of the piezoelectric or electroactive polymer element being fixed to the second piezoelectric or electroactive polymer layer, the first and second ends being connected to the electric circuit (10).

15. A device according to claim 14, characterized in that the first and second piezoelectric or electroactive polymer layers are deposited on a part of the length or the entire length of the inner and outer surfaces of the metal strip (24).