Glass Ceramic Spiral Spring Thermal Stability
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Solution Overview
Problem
Micromechanical components, particularly spiral springs in mechanical watches, face significant accuracy deviations due to temperature fluctuations, as existing materials like silicon and diamond require complex and costly thermal compensation, limiting their use to expensive clocks, and glass-ceramic spiral springs have not met the exact dimension requirements for clockwork components.
Innovation Solution
A spiral spring made from special glass ceramics, such as Zerodur, with a low linear thermal expansion coefficient (0 to 0.5x10^-6 K^-1) and a negative temperature coefficient of the elastic modulus, ensuring minimal changes in restoring force and consistent mechanical properties over a large temperature range, along with a manufacturing process that achieves precise dimensions and low surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If spiral springs are made from silicon or diamond, then manufacturing precision and dimensional accuracy are improved, but device complexity and cost increase due to required thermal compensation processes
Solution Approach 1:
The patent changes the material parameter (thermal expansion coefficient) by selecting glass-ceramic materials with specifically tailored thermal properties. The glass-ceramic composition is designed to have a thermal expansion coefficient that compensates for the positive temperature coefficient of silicon's elastic modulus, achieving temperature compensation through material selection rather than complex processing steps.
Solution Approach 2:
The patent employs composite glass-ceramic materials that combine the advantages of glass (low thermal expansion) and ceramic (mechanical strength and stiffness). This composite material approach provides both the dimensional stability needed for precision manufacturing and the inherent temperature compensation properties, eliminating the need for additional thermal compensation processes.
2Stability of the object's composition
If spiral springs are made from glass-ceramic materials, then thermal stability is improved, but manufacturing precision deteriorates due to inability to achieve exact dimensions
Solution Approach 1:
The patent utilizes the negative temperature coefficient of the elastic modulus of glass-ceramic materials as a key parameter. By selecting materials where this negative coefficient counterbalances the positive coefficient of silicon, the patent achieves temperature compensation while maintaining manufacturability. The material parameters are specifically chosen to provide both thermal stability and dimensional accuracy.
3Stability of the object's composition
If complex thermal compensation processes are applied to silicon springs, then temperature fluctuations are compensated, but productivity decreases and cost increases
Solution Approach 1:
The glass-ceramic material provides self-service temperature compensation through its inherent material properties. The negative temperature coefficient of the elastic modulus automatically counteracts temperature-induced frequency deviations without requiring external compensation mechanisms or additional processing steps. This self-compensating behavior simplifies the manufacturing process and improves productivity.
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 spiral spring exhibits thermally stable and accurate mechanical oscillations, enabling precise clockwork performance without the need for complex thermal compensation, thus improving the accuracy of mechanical watch movements while being cost-effective for broader use.
Implementation Method 1
the spring leaf (101) having a substantially or completely rectangular cross section in the winding direction of the windings, the spring leaf (101) being formed at least partially or completely from a special glass ceramic which has a linear thermal expansion coefficient in the temperature range from -50 to 100 ° C from 0 to 2x10 -6
Implementation Method 2
the negative temperature coefficient of the elastic modulus of SiO 2 counteracts the positive one of Si, so that almost complete temperature compensation can be achieved
Data Source
Figure 1A~1C
Figure 1D
Figure 1E
AI summary
The present invention relates to a spiral spring formed at least partially or completely from special glass ceramics exhibiting a linear coefficient of thermal expansion in the temperature range of -50 to 100°C of 0 to 2 x 10⁻⁶ K⁻¹, in particular of 0 to 0.5 x 10⁻⁶ K⁻¹. The invention also relates to a method for manufacturing such a spiral spring. The spiral spring according to the invention is used for micromechanical transmissions, microgears, and in particular clockwork mechanisms.