LVDT Magnetic Core Structure with Thermal Expansion Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
LVDTs face performance issues due to stress and thermal deformation affecting the magnetic core's linearity and stability, especially in harsh environments like aerospace, where soft magnetic cores are subjected to temperature variations and corrosive substances.
Innovation Solution
A magnetic core structure with a soft magnetic core mounted inside a protective tube, featuring a polymer ball insert with a higher thermal expansion coefficient to reduce surface stresses, and a domed rod or bushing for secure attachment, ensuring minimal stress impact on the magnetic flux transmission area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a soft magnetic core is used in an LVDT, then the magnetic flux transmission is improved, but the core becomes susceptible to stress and thermal deformation affecting linearity and stability
Solution Approach 1:
A protective sleeve made of paramagnetic material is introduced as an intermediary between the soft magnetic core and the external environment. This sleeve protects the core surface from stresses caused by thermal deformations and pressure, while not interfering with the magnetic flux transmission since paramagnetic materials have minimal effect on magnetic fields.
Solution Approach 2:
The protective sleeve is designed with a coefficient of thermal expansion matched to or greater than that of the soft magnetic core. This ensures that during thermal cycles, the sleeve expands more than or at the same rate as the core, preventing compressive stresses from developing on the core surface due to differential thermal expansion.
2Reliability
If a protective sleeve is added to protect the core, then the core is protected from frictional wear and stress, but the device complexity increases
Solution Approach 1:
A thin-walled protective sleeve is used instead of a complex rigid structure. The sleeve is sufficiently thin to minimize added complexity and mass, while still providing adequate protection from frictional wear and environmental stresses. The simplicity of the cylindrical sleeve geometry keeps the structural design straightforward.
3Reliability
If the protective sleeve is made of paramagnetic material, then magnetic flux transmission is maintained, but protection against corrosive substances may be reduced
Solution Approach 1:
The protective sleeve is constructed from composite materials that combine paramagnetic properties with corrosion resistance. For example, a paramagnetic metal alloy may be coated with a corrosion-resistant layer, or a paramagnetic polymer composite may be used that inherently resists corrosion from hydraulic fluids and other harsh environments.
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 enhances the stability and reliability of LVDTs by isolating the core from environmental stresses and maintaining magnetic flux integrity across varying temperatures and conditions.
Implementation Method 1
the ball being formed of an elastic material having a coefficient of thermal expansion greater than that of the core magnetic material
Implementation Method 2
As the magnetic flux of the LVDT electromagnetic circuit is transmitted mainly through the core near the surface
Implementation Method 3
A primary coil is provided with a current which induces current in the secondary coils
Data Source
AI summary
A magnetic core structure for a Linear Variable Differential Transducer (LVDT) comprising an elongate core of magnetic material mounted within a protective tube and means for positioning the core within the protective tube, the means for positioning comprising a ball provided within the protective tube at one end of the core, the ball being formed of an elastic material having a coefficient of thermal expansion selected to compensate the difference in elongation between magnetic core structure components caused by thermal expansion.