Coil-Segmented Displacement Sensor for Linear Key Position Detection

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Solution Overview

Problem

Existing displacement sensors for musical instruments face challenges in generating detection signals with high accuracy based on the displacement of movable members.

Innovation Solution

A displacement sensor design featuring a first coil in a movable member and a second coil with opposing magnetic fields, where the distance between the centers of specific coil parts is configured to enhance the accuracy of detection signals by optimizing the magnetic field interactions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional coil configurations are used for displacement detection, then the device structure is simple, but the detection signal accuracy is insufficient

Engineering Contradiction:
Improvedetection signal accuracyVSAvoidcoil structure complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The first coil is divided into a first part and a second part that generate opposite magnetic fields. The second coil is divided into a third part and a fourth part that also generate opposite magnetic fields. This segmentation allows the magnetic fields to be optimized for better detection accuracy while maintaining a relatively simple overall structure.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Different parts of the coils are configured with specific distance relationships. The first distance between the center of the first part and the center of the second part is greater than the second distance between the center of the third part and the center of the fourth part. This local quality differentiation optimizes the magnetic field distribution in different regions to improve detection accuracy.

Inventive Principle:
Principle #3Local quality

2Adaptability or versatility

If the detection range is extended to cover wider displacement variations, then the adaptability improves, but the detection signal linearity deteriorates

Engineering Contradiction:
Improvedetection rangeVSAvoidsignal linearity
Core Design Contradiction:
Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The coil configuration creates a dynamic magnetic field interaction that adapts to different displacement positions. The opposite magnetic fields from the divided coil parts maintain a more consistent relationship across a wider range of displacements, preserving linearity while extending the effective detection range.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

By changing the geometric parameters of the coil configuration, specifically making the first distance greater than the second distance, the magnetic field distribution is optimized to maintain linearity across a wider displacement range, thereby extending the detection range while preserving measurement precision.

Inventive Principle:
Principle #35Parameter changes

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 sensor achieves improved detection signal accuracy and linearity over a wider range of displacements, enabling precise detection of key positions in electronic musical instruments.

Implementation Method 1

a first coil (51) disposed on a movable member (12) that is displaceable in response to an operation; and a signal generator (60) including a second coil (61) that opposes the first coil (51) and generates a detection signal based on a relative position between the first coil (51) and the second coil (61)

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

the first coil (51) includes a first part (521) and a second part (522) that generate opposite magnetic fields from each other in response to a current being received by the first coil (51), the second coil (61) includes a third part (621) and a fourth part (622) that generate opposite magnetic fields from each other in response to a current being received by the second coil (61)

Methodology Applied
Scientific EffectElectromagnetic field generation: Electromagnet

Data Source

PatentEP4130645B1Displacement sensor and electronic musical instrument
Publication Date: 2025.12.17 YAMAHA CORP
  • EP4130645B1 patent drawingFigure 1~2
  • EP4130645B1 patent drawingFigure 3~4
  • EP4130645B1 patent drawingFigure 5~7

AI summary

A displacement sensor includes: a detectable portion: including a first coil; and being disposed on a movable member that is displaceable in response to an operation; and a signal generator: including a second coil that opposes the first coil; and being configured to generate a detection signal based on a relative position between the first coil and the second coil, in which an overall dimension of the first coil in a first direction differs from an overall dimension of the first coil in a second direction perpendicular to the first direction when viewed in plan view.