Inductive Displacement Sensor Compact Coil Design

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Solution Overview

Problem

Inductive displacement sensors require a large amount of space due to the need for a sensor circuit board that matches the length of the measurement path, limiting their use in applications with restricted installation space, such as motor vehicles.

Innovation Solution

The design involves a first secondary coil with a crossover axis perpendicular to the measurement path and a second secondary coil with a crossover axis parallel to the path, reducing the sensor length to a third of the measurement path, allowing for a more compact inductive displacement sensor that accommodates limited axial space by modulating output signals with target geometry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the sensor circuit board is designed to match the length of the measurement path, then clear measurement signals are obtained, but the sensor length becomes too large for space-constrained applications

Engineering Contradiction:
Improvemeasurement signal clarityVSAvoidsensor length
Core Design Contradiction:
Measurement precisionVSLength of stationary object

Solution Approach 1:

The patent introduces a second spatial dimension by stacking secondary coils in layers above and below the primary coil plane. This three-dimensional coil arrangement allows the sensor to achieve the required measurement precision with a significantly reduced axial length, resolving the contradiction between signal clarity and compact size

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

Multiple secondary coils are nested in different spatial layers around the primary coil, with at least one secondary coil positioned above the primary coil plane and at least one below. This nested configuration maximizes the use of available space while maintaining measurement accuracy

Inventive Principle:
Principle #7Nested doll (Nesting)

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 enables clear position measurement signals with a significantly reduced sensor length, allowing for the use of inductive displacement sensors in space-constrained environments, such as motor vehicles, while maintaining accurate signal output.

Implementation Method 1

Due to a predetermined current flow, the primary coil 8 generates a magnetic field which induces voltages in the windings of the secondary coil 14

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP2947425B1Inductive displacement sensor and piston-cylinder assembly
Publication Date: 2017.07.26 SCHAEFFLER TECHNOLOGIES AG & CO KG
  • EP2947425B1 patent drawingFigure 1
  • EP2947425B1 patent drawingFigure 2~4
  • EP2947425B1 patent drawingFigure 5~6

AI summary

The invention relates to an inductive displacement sensor comprising a coil system with a planar primary coil for generating a magnetic field and at least two superimposed planar secondary coils arranged within the primary coil for sensing the position of a target which is movable along the secondary coils, wherein the secondary coils are configured with crossed windings. In an inductive displacement sensor in which the coil system is significantly shortened, the first secondary coil has a crossing that is perpendicular to the direction of movement of the target, while the second secondary coil has a crossing that runs parallel to the direction of movement of the target, and the target is tapered in its axial extent.