Thermocompensated Silicon Hairspring via Layered Oxide
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Solution Overview
Problem
Mechanical watch spiral springs made of silicon or other non-metallic materials face challenges in temperature variation sensitivity, requiring effective thermal compensation to maintain time measurement precision.
Innovation Solution
A heat-compensated spiral spring design incorporating a monocrystalline silicon portion mechanically bonded to a silicon oxide separation layer, with the option to include a third material, such as polycrystalline silicon, and a manufacturing method that allows for varying orientation and shape of the separation layer to modify bending stiffness and achieve precise thermal compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a spiral spring is made of silicon or other non-metallic materials, then the thermal sensitivity is reduced, but the Young's modulus varies with temperature affecting time measurement precision
Solution Approach 1:
The patent applies composite materials by combining monocrystalline silicon with silicon oxide in a layered structure. The silicon oxide layer is integrated within the spiral spring structure itself, creating a composite material system that compensates for temperature-induced Young's modulus variations while maintaining the low thermal sensitivity of silicon. This composite approach allows the spiral spring to maintain dimensional stability and elastic properties across temperature variations.
Solution Approach 2:
The patent implements local quality by placing silicon oxide layers at specific locations within the spiral spring structure rather than uniformly throughout. The silicon oxide is positioned in internal layers that strategically affect the bending stiffness and thermal compensation at critical stress points, allowing localized modification of material properties to achieve overall thermal stability while maintaining measurement precision.
2Object-affected harmful factors
If a layer of silicon oxide is used for thermal compensation, then temperature variation sensitivity is reduced, but the layer orientation and shape flexibility is limited
Solution Approach 1:
The patent applies segmentation by dividing the silicon oxide thermal compensation layer into multiple separate layers distributed throughout the spiral spring structure. Rather than a single continuous layer, the silicon oxide is segmented into discrete internal layers that can be independently positioned and oriented, providing flexibility in designing the overall spring geometry and stress distribution while maintaining thermal compensation functionality.
Solution Approach 2:
The patent utilizes another dimension by integrating the silicon oxide layers in the thickness dimension of the spiral spring rather than only as surface coatings. This internal layering approach adds a dimensional degree of freedom for controlling thermal compensation, allowing the oxide layers to be positioned at different depths and orientations within the spring structure to achieve desired mechanical and thermal properties.
3Stability of the object's composition
If the separation layer thickness is increased for better thermal compensation, then thermal stability is improved, but the bending stiffness of the spiral spring is reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of silicon oxide layers and the spacing between them. Rather than using a single thick layer, the invention optimizes multiple thinner layers with specific thickness parameters that provide adequate thermal compensation while maintaining the bending stiffness required for proper oscillator function. The layer thickness and spacing are tuned as adjustable parameters to balance thermal stability and mechanical strength.
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 design provides enhanced thermal stability and precision in timekeeping by adjusting the bending stiffness of the spiral spring, reducing its dependence on temperature variations and allowing for high precision in the thickness of the separation layer, thereby improving the accuracy and reliability of mechanical watches.
Implementation Method 1
They use the principle of thermal compensation produced by a layer of silicon oxide. This layer of silicon oxide can be an outer layer, as proposed by patents or patent applications EP 1 422 436, WO 2009/068091 and EP 2 284 629.
Implementation Method 2
the monocrystalline silicon portion is mechanically bonded to the silicon oxide separating layer
Implementation Method 3
The spiral spring is a spiral spring which produces a restoring torque on the balance as soon as the latter is out of a specific position called neutral position
Data Source
Figure 1~3
Figure 4A~4F
Figure 5~13
AI summary
A thermocompensated spiral spring for a mechanical oscillator in a timepiece comprises an elastically flexible strand (2) extending along a spiral line (ℓ). This elastically flexible strand (2) comprises a portion (3) of monocrystalline silicon (A) and a portion (5) of polycrystalline silicon (C) separated from each other by a separating layer (4) of silicon oxide (B). The portion (4) of monocrystalline silicon (A) and the portion (5) of polycrystalline silicon (C) are mechanically bonded to the separating layer. The invention relates to the aforementioned spiral spring, as well as a method for manufacturing this spiral spring.