Accuracy stabilizing device for timepiece and mechanical timepiece provided with same

Abstract

The present invention addresses the problem of providing an accuracy stabilizing device for a timepiece that can stabilize the rate of a timepiece over a long period of time with extremely low power consumption without directly applying mechanical vibrations to a balance while using an external reference.　This accuracy stabilizing device for a mechanical timepiece includes: a detection means for detecting the state of motion of a balance; an actuator which is driven at a frequency twice as high as the natural frequency of the balance on the basis of an output of the detection means and periodically changes a physical parameter of a movable member supporting the balance; and a control circuit which uses an external reference oscillator as a time standard, minutely corrects a drive phase or a duty ratio of the actuator, and adjusts the average rate of the balance.

Description

Accuracy Stabilization Device for Watches and Mechanical Watches Equipped with the Same 【0001】 The present invention relates to a technique for highly accurately stabilizing the pace of a mechanical watch by using parametric excitation for the template (balance pendulum) of the mechanical watch. In particular, it relates to a low-power consumption type accuracy stabilization device that periodically modulates the physical parameters of the template support member at twice the frequency (2F0) of the template natural frequency F0 and performs minute phase correction with respect to an external reference oscillator. 【0002】 In a mechanical watch, the frequency of the template slightly varies due to the torque fluctuation of the mainspring, posture difference, temperature change, etc., resulting in an error in the long-term pace (the progress or delay of time). Although an injection synchronization method that performs forced synchronization based on an external crystal oscillator has been proposed, since an electric signal is directly converted into mechanical vibration and energy is injected into the template, it requires a large driving power and has a problem of deteriorating the Q value of the template. 【0003】 Patent Document 1 discloses a "spring drive" method that controls the rotation period by electronic control means while using a mechanical energy source (mainspring). However, this method virtually eliminates the escapement and equalizes the mainspring drive with a unique control system. 【0004】 Japanese Patent No. 3006593 【0005】 An object of the present invention is to provide an accuracy stabilization device for a watch that can stabilize the pace over a long period with extremely low power consumption without directly injecting mechanical vibration into the template while using an external reference. 【0006】In a first aspect of the present invention, a clock accuracy stabilization device is provided, comprising: a) a detection means for detecting the motion state of the balance wheel; b) an actuator driven at twice the natural frequency of the balance wheel based on the output of the detection means, which periodically changes at least one physical parameter selected from the position, rigidity, mass distribution, or damping coefficient of a movable member supporting the balance wheel; and c) a control circuit that uses an external reference oscillator as a time standard and adjusts the average rate of the balance wheel by slightly correcting the drive phase or duty cycle of the actuator, wherein the signal of the external reference oscillator is not directly converted into mechanical vibration and transmitted to the balance wheel. Here, the external reference oscillator is a device that contains an oscillator that oscillates at a predetermined reference frequency, and is a transmitter that sends out a signal of the reference frequency oscillated by the contained oscillator. 【0007】 The actuator may be at least one selected from a piezoelectric element, a magnetostrictive element, an electrostatic actuator, a shape memory alloy actuator, an electromagnetic coil, or a micromachine actuator. 【0008】 The control circuit may maintain the amplitude of the balance wheel by minimizing at least one drive parameter selected from voltage, current, force, or pulse width to the actuator when the amplitude of the balance wheel is within a set range, and by increasing the drive parameter only when the amplitude goes outside the set range. 【0009】 The control circuit calculates the phase difference between the external reference oscillator and the balance wheel motion, and corrects the average rate by slightly advancing or delaying the drive signal of the actuator according to the phase difference, but it may also be configured so as not to substantially change the total amount of kinetic energy supplied to the balance wheel by the actuator. 【0010】 The actuator may be positioned between the bearing jewel and the bore jewel that support the end of the balance wheel shaft, or on the upper surface of the bearing jewel, and may also serve as a shock absorber by interposing an elastic layer on at least one surface of the actuator. 【0011】Figure 1 is an image diagram showing the accuracy stabilization device for mechanical watches of this embodiment incorporated into the mechanical watch body. Figure 2 is a schematic diagram of a sensor and actuator attached to a conventional vibration mechanism. Figure 3 is a cross-sectional view of the jewel bearing and jewel bearing areas showing the positions where the actuators are placed in a modified arrangement. Figure 4 is a block diagram showing the logic configuration of the control operation of the control unit. 【0012】 This accuracy stabilization device for mechanical watches, which utilizes an external reference but does not directly inject mechanical vibrations into the balance wheel, and can stabilize the rate over a long period with extremely low power consumption, was realized by incorporating an external reference oscillator separate from the balance wheel of the watch to be installed, periodically modulating the physical parameters of the balance wheel support member at twice the frequency of the balance wheel's natural frequency F0 (2F0), and performing minute phase correction with respect to the external reference oscillator. 【0013】 Figure 1 is an image diagram showing the accuracy stabilization device for mechanical watches of this embodiment incorporated into the mechanical watch body. This device is configured as a system in which a sensor 1003, actuator 1004, control unit 1005, external reference oscillator 1006, secondary battery 1007, barrel generator 1008 that generates electricity by controlling the rotation of the barrel, vibration generator 1009, and solar power generation panel 1010 that generates electricity from sunlight, etc. 1011 are added to the mechanical watch body 1001, which has a conventional vibration mechanism 1002 consisting of a balance wheel, hairspring, bridge, jewel bearings, and bearing jewels. The control unit 1005 is electrically connected to the other components to receive detection signals, transmit control signals, and supply power. 【0014】 The conventional vibration mechanism 1002, which is a component of the mechanical watch itself into which the system is to be incorporated, has a sensor 1003 and an actuator 1004 attached to it. Figure 2 is a schematic diagram of the sensor and actuator attached to the conventional vibration mechanism. The sensor 1003 is built into the mechanical watch body 1001 and detects the vibration of the balance wheel 2001. The actuator 1004 is positioned between the mechanical watch body 1001 and the suspension balance bridge 2002 and applies a predetermined vibration. 【0015】(Sensor) Sensor 1003 employs a CMOS optical motion sensor. The sensor used here pulses a predetermined VCSEL (Vertical-Cavity Surface-Emitting Laser) and acquires vibration data of the balance wheel by performing correlation calculations on the scattered light pattern in the light-receiving pixel array, and then transfers the data to the control unit. 【0016】 (Actuator) The piezoelectric element used as actuator 1004 is a multilayer PZT stack, which displaces the balance wheel in the series direction. The drive frequency is 2F0 (8Hz if F0=4Hz). 【0017】 Here, the actuator is positioned between the mechanical watch body and the suspended balance bridge; however, the possible placement methods in this invention are not limited to this. As a variation of the placement method, an arrangement can be adopted in which the actuator is positioned between the bearing jewel and the bore jewel supporting the balance shaft end, or on the upper surface of the bearing jewel, and an elastic layer is interposed on at least one surface of the actuator to also serve as a shock absorber. 【0018】 (Modified Actuator Arrangement Method) Figure 3 is a cross-sectional view of the bearing stone and bore stone portion showing the position where the actuator is placed in a modified arrangement method. The balance shaft 3000 is supported at its shaft end by the bearing stone 3001 and the bore stone 3002. Here, the space between the bearing stone and the bore stone 3003 and the upper surface of the bearing stone 3004 can be used as positions for placing the actuator. When the method of placing the actuator between the bearing stone and the bore stone 3003 is adopted, the actuator displaces the space between the bearing stone and the bore stone in the series direction at a driving frequency 2F0 (8Hz when F0=4Hz). 【0019】 (Control Unit) The control unit 1005 employs a microcontroller unit (hereinafter referred to as MCU). The MCU refers to an external reference and calculates the difference Δφ with the temperature phase using a PLL method, and PI controls the phase δφ of the drive signal so that Δφ becomes zero. 【0020】Figure 4 is a block diagram showing the logic configuration of the control operation of the control unit. The logic of the control operation is formed as a large logic block consisting of a parametric excitation amplitude stabilization logic 4001 and a frequency calibration logic 4002. 【0021】 In the parametric excitation amplitude stabilization logic 4001, the excitation intensity is determined periodically from the frequency and amplitude related to the operation of the balance wheel acquired by the sensor 1003. In the frequency calibration logic 4002, the basic excitation frequency and excitation intensity data generated by the parametric excitation amplitude stabilization logic are received, and the actuator 1004 is repeatedly driven at the frequency modulated and converted by the detailed logic described later, thereby transmitting vibrations to the balance wheel. 【0022】 The details of the parametric excitation amplitude stabilization logic 4001 are as follows: In step A1, the sensor 1003 measures the frequency F0 and amplitude related to the operation of the balance wheel. In step A2, the control unit scrutinizes F0. In step A3, the control unit calculates the basic excitation frequency as F0 x 2. In step A4, the control unit determines the amplitude and the excitation intensity. In step A5, the control unit repeats the operation from step A1 at predetermined intervals. 【0023】 The details of the frequency calibration logic 4002 are as follows: In step B1, the control unit receives the basic excitation frequency and excitation intensity data. In step B2, the control unit receives the reference frequency from the external reference oscillator 1006. In step B3, the control unit compares the data received in B1 with the reference frequency received in B2 and calculates the calibration amount. In step B4, the control unit modulates the basic excitation frequency in proportion to the calibration amount and performs phase conversion. In step B5, the control unit drives the actuator 1004 with the frequency data modulated and phase converted in step B4. In step B6, the control unit repeats the operation from step B1. 【0024】 (Parametric Excitation Theory) The theoretical basis for the effectiveness of the logic in this embodiment is as follows: If the equivalent stiffness of the balance wheel is k(t)=ke[1+ε cos(2ωet+δφ)], then an amplitude gain G≈ε / 2 is obtained within the stable region (ε≪1, ζ≪0.01) in Mathieu's equation. By fine-tuning δφ, the mean angular velocity shifts to ω0+Δω, and Δω / ω0≈(ε / 2) tan(δφ). Using this relationship, the rate can be linearly corrected within a range of ±5s / day. 【0025】 The specifications of the mechanical watch movement and various devices used in this embodiment, as well as the rate stability achieved, are as follows. However, the effectiveness of the present invention is not limited to these specifications and may be modified as appropriate. Movement: 28800 bph, in-house caliber. PZT stack: 0.6 mm in length, 40 layers, maximum displacement 25 nm. Driving voltage: ±10 V, average current 1.8 microamperes. Rate stability: ±0.4 s / day (non-position variable). 【0026】 By providing the accuracy stabilization device described above, it becomes possible to improve the accuracy of existing mechanical watches to a level comparable to quartz watches without removing the balance wheel or escapement. Furthermore, it is possible to significantly improve convenience and reliability without compromising the aesthetics or traditional mechanism of the watch. 【0027】 The present invention can be applied to all mechanical timekeeping devices that require long-term rate stability, including high-end mechanical wristwatches, marine chronometers for ships, and mechanical clocks. 【0028】 1001 Mechanical clock body 1002 Conventional vibration mechanism 1003 Sensor 1004 Actuator 1005 Control unit 1006 External reference oscillator

Claims

1. A precision stabilization device for a mechanical watch, comprising: a) a detection means for detecting the motion state of the balance wheel; b) an actuator driven at twice the natural frequency of the balance wheel based on the output of the detection means, which periodically changes at least one physical parameter selected from the position, rigidity, mass distribution, or damping coefficient of a movable member supporting the balance wheel; and c) a control circuit that uses an external reference oscillator as a time standard and adjusts the average rate of the balance wheel by slightly correcting the drive phase or duty cycle of the actuator, wherein the signal of the external reference oscillator is not directly converted into mechanical vibration and transmitted to the balance wheel.

2. The apparatus according to claim 1, characterized in that the actuator is at least one selected from a piezoelectric element, a magnetostrictive element, an electrostatic actuator, a shape memory alloy actuator, an electromagnetic coil, or a micromachine actuator.

3. The apparatus according to claim 1 or 2, characterized in that the control circuit minimizes at least one drive parameter selected from voltage, current, force, or pulse width to the actuator when the amplitude of the balance wheel is within a set range, and maintains the amplitude of the balance wheel by increasing the drive parameter only when the amplitude goes outside the set range.

4. The apparatus according to claim 1, wherein the control circuit calculates the phase difference between the external reference oscillator and the balance wheel motion, and corrects the average rate by slightly advancing or delaying the drive signal of the actuator according to the phase difference, but does not substantially change the total amount of kinetic energy supplied to the balance wheel by the actuator.

5. The apparatus according to claim 1, wherein the actuator is positioned between the cap jewel supporting the end of the balance wheel shaft and the bearing jewel, or on the upper surface of the bearing jewel, and an elastic layer is interposed on at least one surface of the actuator to also serve as a shock absorber.

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