Resonator Thermocompensated by Shape-Memory Metal Coating
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Solution Overview
Problem
Existing resonators for time or frequency bases, such as those used in watches, face challenges in thermal compensation, requiring complex corrections due to significant frequency drift with temperature changes, especially in the COSC certification range of +8 to +38°C, which complicates their application in electronic quartz watches.
Innovation Solution
A thermally compensated resonator is designed with a core material like glass, metallic glass, or silicon, coated with shape-memory metals like Cu-Zn, Co-Ni, or Ni-Ti alloys, whose Young's modulus variations counteract those of the core, achieving zero or minimal frequency variation with temperature, thereby eliminating the need for complex temperature corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a resonator uses a core material like silicon or quartz, then the resonator provides stable mechanical properties, but the frequency drifts significantly with temperature changes
Solution Approach 1:
The resonator body is constructed as a composite structure with a core material (silicon, quartz, or glass) surrounded by a shape-memory metal coating. This composite configuration allows the core to provide mechanical stability while the coating compensates for thermal effects, achieving both mechanical stability and frequency stability simultaneously.
Solution Approach 2:
The invention exploits the temperature-dependent Young's modulus variation of shape-memory metals. By selecting a coating material whose Young's modulus increases with temperature (positive thermal coefficient) while the core material's Young's modulus decreases (negative thermal coefficient), the system achieves thermal compensation through parameter changes in the composite structure.
2Device complexity
If existing resonators are used without thermal compensation, then the device structure remains simple, but complex electronic corrections are required for COSC certification
Solution Approach 1:
The shape-memory metal coating provides self-service thermal compensation by automatically counteracting temperature-induced frequency drift through its inherent positive Young's modulus thermal coefficient. This passive compensation mechanism eliminates the need for active electronic correction systems, simplifying both the device structure and calibration procedures while enabling COSC certification.
3Reliability
If a shape-memory metal coating is added to compensate for thermal effects, then frequency stability improves, but the manufacturing process becomes more complex
Solution Approach 1:
The shape-memory metal coating is applied selectively to specific surfaces of the resonator body where thermal compensation is most effective. This localized approach maintains manufacturing simplicity by avoiding complete encapsulation, while still achieving the desired frequency stability through targeted thermal compensation at critical locations.
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 effectively stabilizes frequency over a range of temperatures, reducing the need for electronic corrections and enhancing the reliability of time or frequency bases by ensuring minimal thermal coefficient variations, thus improving their performance and simplifying their application.
Implementation Method 1
at least one part of the body comprises at least one shape-memory metal coating whose Young's modulus variations as a function of temperature are of opposite sign to those of the first material
Implementation Method 2
whose Young's modulus variations as a function of temperature are of opposite sign to those of the first material used for the core in order to allow said resonator to have a frequency variation as a function of temperature at least at first order substantially zero
Data Source
Figure 1~7
Figure 5
AI summary
The invention relates to a thermocompensated resonator (1) comprising a body (5) used in deformation, the core (8) of the body (5) being formed from a first material. According to the invention, at least a portion of the body (5) comprises at least one coating (6) of shape-memory metal whose Young's modulus with temperature (CTE) is opposite in sign to that of the first material used for the core (8), so as to allow said resonator to have a frequency variation with temperature that is at least to the first order (α, β) substantially zero. The invention relates to the field of watch components.