Piezoelectric Balance Spring Frequency Control via Resistance Pulses

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Solution Overview

Problem

Existing electronic control systems for mechanical timepieces with piezoelectric balance springs can only reduce oscillation frequency by increasing variable capacitance, leading to suboptimal mechanical movement rates and precision, making them suitable only for average or poor-quality mechanical movements.

Innovation Solution

A control device that uses an auxiliary electronic oscillator to generate control pulses varying the impedance of the piezoelectric balance spring, allowing synchronization of the mechanical oscillator's frequency with a desired frequency through carefully timed resistance changes, thereby correcting temporal drift and maintaining precision without degrading the mechanical movement's initial setting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If variable capacitance is increased to reduce oscillation frequency, then frequency control is achieved, but mechanical movement rate becomes suboptimal and precision degrades

Engineering Contradiction:

Improveoscillation frequencyVSAvoidtimekeeping precision

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent changes the electrical parameter (resistance) instead of the electrical parameter (capacitance) used in prior art. By momentarily varying the electrical resistance produced by the control device between the two electrodes, control pulses are generated that decrease resistance relative to nominal resistance, allowing frequency reduction without degrading the mechanical movement's natural precision

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The control device applies a plurality of control pulses during each of several times, with temporal spacing between pulses equal to a number N multiplied by half a determined control period. This periodic pulsed action allows continuous frequency synchronization while maintaining the mechanical movement's optimal operating characteristics

Inventive Principle:

Principle #19Periodic action

2Adaptability or versatility

If electronic control system is added to mechanical timepiece, then frequency control capability is improved, but mechanical movement's initial setting is degraded

Engineering Contradiction:

Improvefrequency control capabilityVSAvoidmechanical movement precision

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent replaces the mechanical adjustment method with an electronic control approach that uses electrical resistance modulation rather than mechanical changes. The control device momentously varies electrical resistance to generate control pulses that synchronize frequency without physically altering the mechanical movement's optimal setting

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the state of the piezoelectric material from its natural state to a controlled state by applying voltage that varies electrical resistance. This allows the mechanical movement to maintain its optimal mechanical settings while the electrical parameter provides fine frequency adjustment capability

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution enables precise synchronization and correction of the mechanical oscillator's frequency, ensuring optimal operation and maintaining high precision without degrading the mechanical movement's natural characteristics, making it suitable for high-quality timepieces.

Implementation Method 1

the balance spring is at least partially formed by a piezoelectric material and by at least two electrodes arranged to have between them a voltage induced by the piezoelectric material undergoing mechanical stress

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The control device is arranged to be capable of momentarily varying the electrical resistance produced by the control device between the at least two electrodes, in order to generate, at least at times, control pulses which are distinct and each have a certain duration TP, each control pulse consisting of a momentary decrease in said electrical resistance relative to a nominal electrical resistance

Methodology Applied

Scientific EffectElectrical resistance variation: Electrical Resistance

Implementation Method 3

The electronic control device includes an auxiliary oscillator of the electronic type, which is generally more precise than a mechanical oscillator, in particular a quartz oscillator

Methodology Applied

Scientific EffectQuartz oscillation:

Data Source

PatentUS11619910B2Timepiece including a mechanical movement whose operation is controlled by an electronic device

Publication Date: 2023.04.04 THE SWATCH GRP RES & DEVELONMENT LTD

AI summary

A timepiece includes a mechanical oscillator, formed by a balance and a piezoelectric balance spring, and a control device for controlling the frequency of the mechanical oscillator. This control device is arranged to be capable of generating time-separated control pulses, each including a momentary decrease in an electrical resistance applied by the control device between two electrodes of the piezoelectric balance spring relative to a nominal electrical resistance. The control device is arranged to be capable of applying a plurality of control pulses during each time of a series of distinct correction times or without interruption in a continuous time window, in order to respectively synchronize the mechanical oscillator at a correction frequency whose value depends on a detected positive or negative temporal drift or at a desired frequency for the mechanical oscillator.