Tapered Inductor Core Surface Design for Reliable Electronic Pens

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Solution Overview

Problem

Existing electronic pens for position detection in input devices face issues with surface damage and coil disconnection due to the sharp edges and high surface roughness of traditional inductor cores, which affect accuracy and reliability.

Innovation Solution

A tubular inductor core with a tapered inclined portion and a coaxial straight trunk portion, featuring a convex curved connection and reduced surface roughness, is designed to minimize damage and enhance position detection accuracy, incorporating a magnetic material with controlled crystal grain size and distribution for improved reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional inductor core with sharp edges and high surface roughness is used, then the manufacturing process is simpler, but the surface causes damage and coil disconnection reducing reliability

Engineering Contradiction:

ImprovereliabilityVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The inductor core applies local quality by creating different surface roughness characteristics in different regions. The tip portion has a first surface roughness while the base portion has a second surface roughness, allowing the tip to minimize damage while the base provides stable coil winding. This regional differentiation resolves the contradiction by optimizing each area for its specific function.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The inductor core transitions from sharp edges to curved surfaces through the tip portion design. The curved surface replaces traditional sharp edges, reducing stress concentration and surface damage while maintaining manufacturing feasibility. This curvature principle directly addresses the reliability issue caused by sharp edges.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Measurement precision

If the inductor core has high surface roughness, then manufacturing is easier, but position detection accuracy deteriorates

Engineering Contradiction:

Improveposition detection accuracyVSAvoidsurface finish requirement

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent applies local quality by specifying different surface roughness requirements for different regions. The tip portion (first region) has controlled surface roughness to minimize damage and improve detection accuracy, while the base portion (second region) can have higher roughness for easier manufacturing. This regional approach resolves the contradiction between manufacturing ease and detection precision.

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If the inductor core has sharp edges, then manufacturing is simpler, but stress concentration occurs leading to surface damage

Engineering Contradiction:

Improvesurface damageVSAvoidedge geometry

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The tip portion of the inductor core is designed with a curved surface instead of sharp edges. This curvature eliminates stress concentration points that cause surface damage, while the curved geometry can be achieved through standard manufacturing processes like injection molding or machining, minimizing the impact on manufacturing simplicity.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The curved tip portion acts as a cushioning element that distributes and reduces stress before it reaches the core structure. By designing this protective curved geometry in advance, the patent prevents surface damage before it occurs, resolving the contradiction between manufacturing simplicity and damage prevention.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 inductor core design reduces the risk of surface damage and coil disconnection, improving position detection accuracy and reliability by distributing stress and maintaining high magnetic permeability.

Implementation Method 1

Detection between the position detection sensor and the electronic pen is enabled with the position detection device, through transmission and reception of a position detection signal by a coupling method such as an electromagnetic inductive coupling method

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11894170B2Inductor core, electronic pen core portion, electronic pen, and input device

Publication Date: 2024.02.06 KYOCERA CORP

AI summary

An inductor core includes: a tubular magnetic material body formed of magnetic material. The tubular magnetic material body includes an inclined portion including an inclined surface which constitutes a peripheral surface of a truncated cone having an outer diameter that increases from one end toward the other end of the tubular magnetic material body; and a straight trunk portion which is disposed coaxially with the inclined portion, includes an outer peripheral surface which constitutes a peripheral surface of a cylindrical body, and is connected with the inclined portion. An arithmetic mean roughness Ra of a region in the outer peripheral surface of the straight trunk portion which region is in a vicinity of the other end, is smaller than an arithmetic mean roughness Ra of a region in the outer peripheral surface of the straight trunk portion which region is in a vicinity of the inclined portion.