Inductive Sensor Coil-Core Layout for Temperature-Stable Accuracy
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Solution Overview
Problem
Existing inductive proximity or distance sensors face challenges in achieving high accuracy and reliability, particularly in environments with temperature fluctuations, where known constructions do not adequately address sensitivity and cost-effectiveness.
Innovation Solution
The design incorporates a coil carrier with a coil winding and a core that extends beyond an axial contact surface, using a core with a rectangular cross-sectional profile and a U-core configuration, which is pressed onto a second axial contact surface using an elastic force, ensuring stability and accuracy across temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sensor constructions are used, then basic functionality is achieved, but accuracy and reliability are insufficient particularly under temperature fluctuations
Solution Approach 1:
The core is divided into multiple core sections (first core section, second core section, third core section) with different cross-sectional profiles. Each section serves a specific function: the first section with rectangular profile provides magnetic coupling, the second section with rounded profile reduces stress concentration, and the third section provides additional magnetic path. This segmentation allows optimization of each section for its specific purpose, improving overall sensor accuracy and reliability.
Solution Approach 2:
Different sections of the core have different local qualities in terms of cross-sectional profile. The rectangular profile sections provide efficient magnetic coupling with the coil winding, while the rounded profile section provides stress relief and better mechanical properties. This local differentiation of quality allows the core to simultaneously achieve high magnetic efficiency and mechanical reliability.
2Measurement precision
If the core extends beyond the axial contact surface to improve magnetic coupling, then sensitivity increases, but manufacturing complexity increases
Solution Approach 1:
The core sections are designed as thin-walled hollow structures rather than solid blocks. This allows the core to extend axially beyond the contact surface for improved magnetic coupling while keeping the overall volume and material usage low. The thin-walled construction simplifies manufacturing processes such as stamping and forming, making the extended geometry economically feasible.
Solution Approach 2:
The core is constructed from multiple material sections with different properties - some sections with rectangular profiles for optimal magnetic coupling and others with rounded profiles for stress relief. This composite approach allows each section to be optimized for its specific function while maintaining manufacturability through standardized forming processes.
3Measurement precision
If temperature compensation mechanisms are added to maintain accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The core sections with different cross-sectional profiles and the coil carrier are designed with appropriate thermal expansion characteristics. The rounded profile sections and the overall geometry are configured to compensate for thermal expansion effects, maintaining the axial alignment between the coil winding and core sections across a wide temperature range. This passive thermal compensation achieves temperature stability without adding active control mechanisms.
Solution Approach 2:
The sensor structure itself provides temperature compensation through its geometric design. The specific configuration of core sections with different profiles and their arrangement relative to the coil carrier creates a self-compensating system that maintains measurement accuracy across temperature variations without requiring external temperature sensors or control systems.
4Measurement precision
If a solid core profile is used, then sensitivity is maximized, but manufacturing cost and weight increase
Solution Approach 1:
The core sections are constructed as thin-walled hollow structures rather than solid blocks. This dramatically reduces the weight and material usage while maintaining the axial extension beyond the contact surface. The thin-walled construction preserves the magnetic coupling effectiveness because the magnetic flux primarily travels through the high-permeability core material walls rather than requiring solid filling of the entire volume.
Solution Approach 2:
The core is segmented into multiple sections with different wall thicknesses and profiles. Some sections have thicker walls for optimal magnetic coupling, while others have thinner walls for weight reduction. This segmentation allows optimization of the weight-st sensitivity trade-off in different regions of the core.
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 sensor's sensitivity, accuracy, and reliability while being cost-effective and easy to produce, maintaining precision independently of temperature fluctuations.
Implementation Method 1
at least one coil carrier (7) with a coil winding (8) located thereon for generating a magnetic field
Data Source
AI summary
The sensor e.g. inductive proximity or distance sensor (1), has an inductive sensing unit (5) including a coil support (7) with a coil winding (8) for generating a magnetic field and a U-shaped core (9). The winding is directly extended in axial direction adjacent to an axial contact surface of the support. The core is partially arranged in a recess in the support, and lies on another axial contact surface perpendicular to the former axial contact surface. A core section of the core comprises a rectangular cross sectional profile i.e. opened hollow profile, and is overlapped with the winding.