Tuning Fork Oscillator Material Gradient for Mechanical Watch Precision
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Solution Overview
Problem
Mechanical timepieces face limitations in achieving high precision due to the quality factor of balance-springs, which are close to their limits, and existing tuning fork oscillators in mechanical watches often induce undesired symmetrical oscillations when using materials with low internal friction like monocrystalline silicon.
Innovation Solution
A tuning fork-type oscillator is designed with a material combination that favors antisymmetrical oscillations by using a material with low internal friction for the blades and base, and a material with higher internal friction for the rod and attachment, specifically to dampen symmetrical oscillations and enhance the quality factor of the desired oscillation mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a material with low internal friction (e.g., monocrystalline silicon) is used for the tuning fork oscillator, then the quality factor of the oscillator is increased, but symmetrical oscillations are induced which degrade timekeeping accuracy
Solution Approach 1:
The patent applies local quality by using a material with low internal friction (monocrystalline silicon) specifically for the oscillator assembly (blades and base) to maximize quality factor, while using a different material with higher internal friction for the rod and attachment points to suppress symmetrical oscillations. This localized material differentiation resolves the contradiction by optimizing each component's material properties for its specific functional requirement.
Solution Approach 2:
The patent employs composite materials by combining monocrystalline silicon for the oscillator blades and base with a contrasting material for the rod and attachment structure. This composite approach allows the system to simultaneously achieve high quality factor from the silicon portion while using the contrasting material's higher internal friction to dampen unwanted symmetrical oscillation modes, thereby resolving the accuracy-quality factor trade-off.
2Manufacturing precision
If the balance wheel and hairspring are optimized to increase quality factor, then timekeeping precision is improved, but the quality factor approaches a fundamental limit of approximately 300
Solution Approach 1:
The patent replaces the traditional balance wheel and hairspring mechanical oscillator system with a tuning fork oscillator made of monocrystalline silicon. This substitution enables achievement of quality factors exceeding 300, thereby breaking the fundamental limit that constrains conventional balance-spring mechanisms and enabling superior timekeeping precision.
Solution Approach 2:
The patent fundamentally changes the oscillator parameters by transitioning from a balance wheel-hairspring system to a tuning fork configuration made of monocrystalline silicon. This parameter change includes altering the material composition (to single-crystal silicon), the geometric configuration (tuning fork shape), and the oscillation mode (antisymmetric vibration), collectively enabling quality factors that surpass the 300 limit of traditional mechanisms.
3Duration of action of moving object
If magnets are used to distribute energy to the oscillator or regulate energy, then the oscillator can be sustained, but the system is no longer purely mechanical as magnetic forces are electromagnetic
Solution Approach 1:
The patent applies self-service by designing the tuning fork oscillator to sustain its own oscillations through purely mechanical means without requiring external magnetic or electronic systems. The oscillator's high quality factor monocrystalline silicon construction allows it to maintain oscillations for extended periods through its own stored energy, eliminating the need for magnetic sustenance mechanisms and preserving mechanical purity while achieving long duration of action.
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
This design significantly increases the quality factor of the oscillator, favoring antisymmetrical oscillations and reducing the quality factor of symmetrical oscillations, thereby improving the precision of mechanical timepieces without relying on electronic or magnetic interactions.
Implementation Method 1
a material with higher internal friction for the rod and attachment, specifically to dampen symmetrical oscillations
Implementation Method 2
the oscillator being capable of oscillating in a desired antisymmetric mode as well as in an undesired symmetric mode
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
The present invention relates to a wristwatch comprising a mechanical clock movement with a resonator of the tuning fork type. The oscillator preferably comprises a material A having low internal friction. In the oscillator of the invention, undesired symmetric oscillations are avoided, for example, through the choice of the materials from which the tuning fork is made. According to preferred embodiments, the stem and/or fixing of the oscillator comprises a material having internal friction that is greater than that of said material A, so that the quality factor Q2 of the symmetric oscillations is reduced, unlike the quality factor Q1 of the antisymmetric oscillation mode.