Nb-Mo Hairspring Composition for Stable Timepiece Rate Accuracy
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Solution Overview
Problem
Existing mechanical timepieces using Nb—Mo alloys for hairsprings face challenges in achieving stable time accuracy due to uncontrolled temperature changes, as the Young's modulus and thermal expansion are difficult to manage, leading to unpredictable rate changes.
Innovation Solution
A hairspring made of a Nb—Mo alloy with a specific Mo content range (5% to 14% at%) and controlled deformation texture, along with a first and second oxide coating film layer, to stabilize the temperature coefficient of elasticity (TCE) and minimize rate changes over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If Nb—Mo alloy is used for hairspring, then thermal expansion ratio is reduced, but temperature coefficient of elasticity (TCE) becomes difficult to control
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Mo content within 5-14 at% range and adjusting processing parameters (processing rate 5-20%, thermal processing temperature 500-900°C) to achieve the desired TCE. This quantitative control of composition and process parameters transforms the uncontrollable TCE into a manageable property.
Solution Approach 2:
The patent utilizes controlled porosity through the creation of deformation texture with specific crystal orientation ({001} plane parallel to wire surface) and controlled residual strain. This internal structural organization acts as a mechanism to stabilize TCE, similar to how controlled porosity can stabilize material properties.
2Manufacturing precision
If Mo content is increased to reduce TCE, then TCE decreases, but manufacturing complexity increases
Solution Approach 1:
The patent simplifies the complexity by establishing a clear parameter range (5-14 at% Mo) with optimal sub-ranges (9-13 at% Mo, preferably 10-12 at% Mo). This defined parameter space reduces the complexity of composition control compared to unbounded optimization.
Solution Approach 2:
The patent applies preliminary action by pre-determining the optimal Mo content range and processing parameters before actual manufacturing. The composition and processing conditions are designed in advance to achieve the desired TCE, eliminating the need for complex post-manufacturing adjustments.
3Manufacturing precision
If processing rate and thermal processing temperature are adjusted to control residual strain, then TCE control improves, but manufacturing process complexity increases
Solution Approach 1:
The patent manages processing complexity by defining specific parameter ranges: processing rate of 5-20% and thermal processing temperature of 500-900°C. These quantified ranges transform complex process control into manageable parameter specifications.
Solution Approach 2:
The patent applies preliminary action by pre-establishing the relationship between processing parameters and residual strain outcomes. The optimal processing conditions are determined in advance to achieve the desired deformation texture and residual strain state, simplifying the actual manufacturing process.
4Manufacturing precision
If oxygen content is precisely controlled in Nb—Mo alloy, then TCE adjustment is possible, but manufacturing difficulty increases
Solution Approach 1:
The patent shifts from controlling oxygen content (which is difficult) to controlling Mo content within a broader range (5-14 at%). This parameter substitution makes the manufacturing process easier while achieving the same TCE control objective.
Solution Approach 2:
The patent uses Mo as a controllable substitute for oxygen control. Mo is easier to control in terms of composition and provides a more straightforward mechanism for TCE adjustment compared to interstitial oxygen, effectively replacing a difficult-to-control element with an easier-to-control one.
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 provides a hairspring with a stable TCE, ensuring minimal rate changes and high accuracy by adjusting Mo content, deformation texture, and incorporating oxide coating layers, resulting in a timepiece movement and timepiece with enhanced stability and precision.
Implementation Method 1
when a temperature change occurs, the specific frequency of the assembly oscillator changes and the accuracy of the timepiece becomes unstable because of changes in thermal expansion of the hairspring and a balance wheel and a Young's modulus of the hairspring
Implementation Method 2
Young's modulus of the hairspring
Implementation Method 3
a first and second oxide coating film layer, to stabilize the temperature coefficient of elasticity (TCE)
Data Source
AI summary
An object of the present invention is to provide a hairspring, a timepiece movement, and a timepiece. A hairspring according to the present invention is characterized by being made of a Nb—Mo alloy containing 5% or more and 14% or less of Mo in at %. Alternatively, a hairspring according to the present invention is characterized by being made of a Nb—Mo alloy containing 5% or more and 14% or less of Mo in at %, inevitable impurities and balance Nb. It is preferable that the hairspring has a deformation texture and a region having a <110>∥{001} orientation degree in a cross section is 30% or more of an entire cross-sectional area.