Clock accuracy stabilization device and mechanical clock equipped with the same

Abstract

An object of the present invention is to provide a timepiece accuracy stabilizing device that uses an external reference but does not directly inject mechanical vibrations into the balance, and that can stabilize the rate over a long period of time with extremely low power consumption. [Solution] An accuracy stabilization device for a mechanical timepiece, comprising: detection means for detecting the motion state of the balance; an actuator that is driven at twice the balance's natural frequency based on the output of said detection means and that periodically changes the physical parameters of a movable member that supports the balance; and a control circuit that uses an external reference oscillator as a time standard and minutely corrects the drive phase or duty ratio of said actuator to adjust the average rate of the balance.

Description

[Technical Field]

[0001] This invention uses parametric excitation to the balance (balanced pendulum) of a mechanical watch to measure the rate. This technology is aimed at achieving high-precision stabilization. In particular, it is aimed at achieving a frequency twice the balance's natural frequency F0 ( 2F0 ) periodically modulates the physical parameters of the balance support and generates minute position signals relative to an external reference oscillator. This invention relates to a low-power consumption precision stabilizing device that performs phase correction. [Background technology]

[0002] In mechanical watches, slight fluctuations in the balance wheel frequency due to torque fluctuations in the mainspring, positional differences, temperature changes, etc. cause errors in the long-term rate (gain / loss of time). An injection locking method has been proposed, which performs forced synchronization using an external crystal oscillator as the reference, but because it directly converts electrical signals into mechanical vibrations and injects energy into the balance wheel, it requires a large amount of driving power and has the problem of degrading the balance wheel's Q value.

[0003] Patent Document 1 discloses a "spring drive" system that uses a mechanical energy source (spring) and controls the rotation period with electronic control means. However, this method effectively eliminates the escapement and uses a unique control system to time the mainspring drive. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3006593 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a timepiece accuracy stabilizing device that uses an external reference but does not directly inject mechanical vibrations into the balance, and that can stabilize the rate over a long period of time with extremely low power consumption. [Means for solving the problem]

[0006] In a first aspect of the present invention, a mechanical timepiece includes: a) a detection means for detecting the motion state of the balance; b) an actuator that is driven at twice the natural frequency of the balance based on the output of the detection means and that periodically changes at least one physical parameter selected from the position, rigidity, mass distribution, or damping coefficient of a movable member that supports the balance; c) a control circuit that uses an external reference oscillator as a time standard and minutely corrects the drive phase or duty ratio of the actuator to adjust the average rate of the balance; and a timepiece accuracy stabilizing device characterized in that the signal from the external reference oscillator is not directly converted into mechanical vibration and transmitted to the balance. Here, the external reference oscillator is a device that includes 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 included 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, and a micromachine actuator.

[0008] The control circuit may minimize at least one drive parameter selected from voltage, current, force, or pulse width to the actuator when the amplitude of the balance is within a set range, and maintain the amplitude of the balance by increasing the drive parameter only when the amplitude is outside the set range.

[0009] The control circuit may calculate a phase difference between the external reference oscillator and the balance movement and slightly advance or delay the drive signal for the actuator in accordance with the phase difference to correct the average rate, without substantially changing the total amount of kinetic energy imparted to the balance by the actuator.

[0010] The actuator may be disposed between the jewel supporting the end of the balance shaft and the hole jewel or on the top surface of the jewel, and an elastic layer may be interposed on at least one surface of the actuator to also serve as a shock absorbing function. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is an image diagram showing a state in which the accuracy stabilizing device for a mechanical timepiece of this embodiment is incorporated into the main body of a mechanical timepiece. [Figure 2] Figure 2 is a schematic diagram of a sensor and actuator attached to a conventional vibration mechanism. [Figure 3] FIG. 3 is a cross-sectional view of the area of ​​the end stone and the hole stone, showing the positions where the actuators are arranged in a modified arrangement method. [Figure 4] FIG. 4 is a block diagram showing the logic configuration of the control operation of the control unit. DETAILED DESCRIPTION OF THE INVENTION

[0012] This precision stabilizing device for mechanical watches uses an external reference but does not directly inject mechanical vibrations into the balance, and can stabilize the rate over a long period of time with extremely low power consumption. It incorporates an external reference oscillator separate from the balance of the watch it is installed in, and generates a frequency twice the balance's natural frequency F0 ( 2F0 This is achieved by periodically modulating the physical parameters of the balance support using a time-domain time-domain oscillator (TOS) to provide minute phase corrections to the external reference oscillator. [Example]

[0013] FIG. 1 is an image diagram showing a state in which the accuracy stabilizing device for a mechanical timepiece of this embodiment is incorporated into the main body of a mechanical timepiece. This device is configured as a system in which a mechanical watch body 1001 having a conventional oscillation mechanism 1002 consisting of a balance wheel, hairspring, bridge, hole jewel, and jewel bearing is added with a sensor 1003, an actuator 1004, a control unit 1005, an external reference oscillator 1006, a secondary battery 1007, a barrel generator 1008 that generates electricity by controlling the rotation of the barrel, a vibration generator 1009, and a solar power generation panel 1010 that generates electricity by receiving sunlight, etc. 1011. The control unit 1005 is electrically connected to the other components to receive sensing signals, send control signals, and provide power.

[0014] A sensor 1003 and an actuator 1004 are attached to a conventional vibration mechanism 1002, which is a component of the mechanical watch itself into which the mechanism is to be incorporated. Figure 2 is a schematic diagram of a sensor and actuator attached to a conventional vibration mechanism. Sensor 1003 is built into mechanical watch body 1001 and detects the vibration of balance wheel 2001. Actuator 1004 is placed between mechanical watch body 1001 and suspended balance cock 2002 and applies a predetermined vibration.

[0015] (sensor) A CMOS optical motion sensor is used for sensor 1003. The sensor used here pulse-drives a specified VCSEL (Vertical-Cavity Surface-Emitting Laser) and performs correlation calculations on the scattered light pattern with a light-receiving pixel array to obtain vibration data of the balance wheel and transfer the data to the control unit.

[0016] (actuator) The piezoelectric element used as the actuator 1004 is a multi-layer PZT stack, which displaces the balance cock in the serial direction. The driving frequency is 2F0 (8Hz when F0=4Hz).

[0017] Here, the actuator is positioned between the mechanical timepiece body and the suspended balance cock, but the positioning methods that can be used in the present invention are not limited to this. As a variation of the arrangement method, an arrangement method can be adopted in which the actuator is arranged between the jewel supporting the end of the balance shaft and the hole jewel or on the top surface of the jewel, and an elastic layer is interposed on at least one surface of the actuator, thereby also providing a shock absorbing function.

[0018] (Modification of actuator arrangement method) 3 is a cross-sectional view of the area of ​​the end jewel and the hole jewel, showing the position where the actuator is to be arranged in a modified arrangement. The end of the balance shaft 3000 is supported by the end jewel 3001 and the hole jewel 3002. Here, the position where the actuator can be arranged can be between the end jewel and the hole jewel 3003 or on the top surface of the end jewel 3004. When the method of placing the actuator between the receiving stone and the hole stone 3003 is adopted, the actuator moves in series between the receiving stone and the hole stone at the drive frequency 2F0 (If F0=4Hz, the displacement is 8Hz).

[0019] (control unit) A microcontroller unit (hereinafter referred to as MCU) is used for the control unit 1005. The MCU refers to an external reference, calculates the difference Δφ from the balance phase using the PLL method, and performs PI control of the phase δφ of the drive signal so that Δφ becomes zero.

[0020] FIG. 4 is a block diagram showing the logic configuration of the control operation of the control unit. The control operation logic is formed as a large logic block from a parametric excitation amplitude stabilization logic 4001 and a frequency calibration logic 4002.

[0021] Parametric excitation amplitude stabilization logic 4001 periodically repeats determining excitation strength from the frequency and amplitude related to the operation of the balance wheel acquired by sensor 1003 . The frequency calibration logic 4002 receives the basic excitation frequency and excitation intensity data generated by the parametric excitation amplitude stabilization logic, and repeatedly drives the actuator 1004 at a frequency modulated and converted by the detailed logic described below, thereby transmitting vibration to the balance cock.

[0022] Details of the parametric excitation amplitude stabilization logic 4001 are as follows. In step A1, the frequency related to the operation of the balance wheel is measured by the sensor 1003. F0 and the amplitude is measured. In step A2, F0 is examined by the control unit. In step A3, the control unit calculates the fundamental excitation frequency as F0x 2. In step A4, the control unit judges the amplitude and determines the excitation strength. In step A5, the control unit repeats the operations from step A1 at a predetermined period.

[0023] The details of the frequency calibration logic 4002 are as follows: In step B1, fundamental excitation frequency and excitation intensity data is received by the control unit. In step B2, a reference frequency is received by the control unit from the external reference oscillator 1006. In step B3, the control unit compares the data received at B1 with the reference frequency received at B2 and calculates the calibration amount. In step B4, the control unit modulates the fundamental 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 operations from step B1.

[0024] (Parametric Excitation Theory) The theoretical basis for the effectiveness of the logic of this embodiment is as follows. If the equivalent stiffness of the balance is k(t)=ke[1+ε cos(2ωet+δφ)], then the amplitude gain G≒ε / 2 is obtained within the stable region of the Mathieu equation (ε≪1, ζ≪0.01). Fine-tuning δφ shifts the average angular velocity to ω0+Δω, and Δω / ω0≒(ε / 2) tan(δφ). Using this relationship, the rate can be linearly corrected within a range of ±5 seconds / day.

[0025] The specifications of the mechanical watch movement and various devices used in this example, as well as the rate stability achieved, are as follows, but the effectiveness of the present invention is not limited to these and may be modified as appropriate. Movement: 28800 bph, in-house caliber. PZT stack: length 0.6mm , number of layers 40 layers , Maximum displacement 25nm. Drive voltage: ±10V, Average current 1.8 microamps . Rate stability: ±0.4s / day (non-posture variable).

[0026] By providing the above-mentioned accuracy stabilizing device, it is possible to improve the accuracy of existing mechanical watches to a level comparable to that of quartz watches without removing the balance or escapement of the watch. It is also possible to significantly improve convenience and reliability without compromising the aesthetics or traditional mechanism of the watch. [Industrial Applicability]

[0027] The device of the present invention can be applied to all mechanical timepieces that require long-term rate stability, such as marine chronometers for ships and mechanical clocks, in addition to high-end mechanical wristwatches. [Explanation of symbols]

[0028] 1001 Mechanical watch body 1002 Conventional vibration mechanism 1003 Sensor 1004 Actuator 1005 control unit 1006 External Reference Oscillator

Claims

1. In a precision stabilizing device for a mechanical watch, a) a detection means for detecting the motion state of the balance; b) an actuator that is driven at twice the natural frequency of the balance based on the output of the detection means and that periodically changes at least one physical parameter selected from the position, rigidity, mass distribution, or damping coefficient of a movable member that supports the balance; c) a control circuit that uses an external reference oscillator as a time standard and minutely corrects the drive phase or duty ratio of the actuator to adjust the average rate of the balance; and wherein the signal of said external reference oscillator is not directly converted into mechanical vibration and transmitted to the balance.

2. 2. The device according to claim 1, wherein the actuator is at least one selected from the group consisting of a piezoelectric element, a magnetostrictive element, an electrostatic actuator, a shape memory alloy actuator, an electromagnetic coil, and a micromachine actuator.

3. 3. The device according to claim 1, wherein 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 is within a set range, and increases the drive parameter only when the amplitude is outside the set range, thereby maintaining the amplitude of the balance.

4. 2. The device according to claim 1, wherein the control circuit calculates a phase difference between the external reference oscillator and the balance movement and slightly advances or delays the drive signal for the actuator in accordance with the phase difference to correct the average rate, without substantially changing the total amount of kinetic energy imparted by the actuator to the balance.

5. A device as described in claim 1, characterized in that the actuator is positioned between the cap jewel supporting the end of the balance shaft and the jewel or on the top surface of the jewel, and that an elastic layer is interposed on at least one surface of the actuator, thereby also providing a shock absorption function.

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