Multilayer Excitation Ring for Thermal Stress Reduction
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Solution Overview
Problem
Transducers face accuracy reduction due to thermally-induced stresses caused by mismatched coefficients of thermal expansion (CTE) between proof mass assemblies and magnetic circuit assemblies, leading to warping and displacement of the proof mass assembly.
Innovation Solution
The implementation of multi-layer excitation rings with dissimilar materials, where each layer's CTE is matched to either the proof mass assembly or the magnet, reduces radial stresses by minimizing CTE mismatches and maintaining a stable magnetic flux profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-material excitation ring is used, then the device complexity is low, but thermally-induced radial stresses occur due to CTE mismatch between the excitation ring and the magnet/proof mass assembly
Solution Approach 1:
The excitation ring is constructed as a composite structure with multiple layers of different materials. Each layer has a specific coefficient of thermal expansion (CTE) matched to either the magnet or the proof mass assembly. This composite construction allows the excitation ring to accommodate thermal expansion differences between components, reducing thermally-induced radial stresses while maintaining measurement accuracy.
Solution Approach 2:
Different portions of the excitation ring are made from different materials with different CTE properties. The first layer is made from a material with a first CTE matched to the magnet, while the second layer is made from a material with a second CTE matched to the proof mass assembly. This local differentiation of material properties allows each interface to experience minimized thermal stress.
2Reliability
If dissimilar materials with different CTE are used for the excitation ring layers, then the CTE mismatch with magnet and proof mass assembly is reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent employs composite materials with specifically selected CTE properties for each layer. The first layer uses a material with CTE matched to the magnet, and the second layer uses a material with CTE matched to the proof mass assembly. This composite approach reduces thermal stress at both interfaces while the layers are manufactured and assembled using conventional techniques.
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 configuration significantly reduces thermally-induced radial stresses, minimizing distortion and error in the transducer's measurement output, thereby enhancing the accuracy and reliability of the transducer.
Implementation Method 1
Each layer of the excitation ring has a coefficient of thermal expansion (CTE) that is matched to either the proof mass assembly or the magnet. A temperature change of the transducer may produce radial stresses between the excitation ring and either magnet or the proof mass assembly due to CTE mismatches between the excitation ring and the respective magnet or proof mass assembly.
Implementation Method 2
Each magnetic circuit assembly includes a magnet for generating a magnetic field and an excitation ring for providing a magnetic return path of the magnetic field.
Data Source
AI summary
The disclosure describes a magnetic circuit assembly that includes a magnet assembly and an excitation ring. The magnet assembly defines a central axis and includes a pole piece and a magnet underlying the pole piece. The excitation ring includes a base and an outer ring positioned around the magnet assembly. The base includes a platform layer underlying the magnet, an upper base layer underlying the platform layer, and a lower base layer underlying the upper base layer. The outer ring overlies the upper base layer and is configured to couple to an outer radial portion of a proof mass assembly. The platform layer and lower base layer are made from high coefficient of thermal expansion (CTE) materials, while the upper base layer and outer ring are made from low CTE materials. Each relatively high CTE material has a higher CTE than each relatively low CTE material.