Active Stylus Magnet Layout for Haptics and Inductive Charging

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Solution Overview

Problem

Existing active styluses face interference between magnetic attachment fields and haptic motor operation, and there is a need for a design that allows for both magnetic attachment and haptic feedback without compromising functionality.

Innovation Solution

A moveable magnet is integrated within the stylus housing, functioning both for magnetic attachment to a device and providing haptic feedback, driven by a haptic motor coil to cause vibration, while being positioned to minimize interference with inductive charging.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a magnet is used for magnetic attachment to a device, then attachment strength is improved, but haptic motor operation is interfered with

Engineering Contradiction:
Improvemagnetic attachment strengthVSAvoidhaptic motor operation
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The patent divides the magnetic attachment function and haptic motor function into spatially separated components. The magnet is positioned at one end of the stylus for magnetic attachment, while the haptic motor coil is positioned at a different location, reducing magnetic interference between the two functions.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent extracts the magnet from the haptic motor assembly, allowing independent positioning of the magnet away from the haptic motor coil. This separation enables the magnet to perform attachment without interfering with haptic motor operation.

Inventive Principle:
Principle #2Taking out (Extraction)

2Strength

If a magnet is positioned for magnetic attachment, then attachment functionality is improved, but inductive charging is interfered with

Engineering Contradiction:
Improvemagnetic attachment strengthVSAvoidinductive charging
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The patent segments the stylus into distinct functional zones: the magnet is positioned at one end for attachment, the inductive charging coil is positioned in the middle section, and the haptic motor is positioned separately. This spatial segmentation allows each function to operate without interfering with the others.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent arranges components along the longitudinal axis of the stylus, utilizing the length dimension to separate magnetic attachment (at the end), inductive charging (in the middle), and haptic feedback (separately positioned) functions, minimizing electromagnetic interference between them.

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

3Reliability

If the inductive charging coil is positioned for charging, then charging capability is improved, but magnetic attachment is interfered with

Engineering Contradiction:
Improveinductive charging capabilityVSAvoidmagnetic attachment strength
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The patent positions the inductive charging coil in the middle section of the stylus, separated from the magnet at the end and the haptic motor at another location. This segmentation ensures that the charging coil does not interfere with magnetic attachment while maintaining charging capability.

Inventive Principle:
Principle #1Segmentation

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 design enables effective magnetic attachment and enhances user tactile sensation by allowing for precise control of haptic feedback, reducing wear and tear, and maintaining efficient charging capabilities.

Implementation Method 1

An inductive charging coil may be mounted within the elongate housing... configured to inductively couple with an output coil of the electronic device in order to receive power from the output coil

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

A magnet configured to magnetically hold the inductive charging coil in a charging position and orientation relative to an inductive charger

Methodology Applied
Scientific EffectMagnetic force: Magnetism

Implementation Method 3

the haptic component may be a movable mass, a magnet, a ferromagnetic element... the coil may be configured to inductively couple with an output coil of the electronic device in order to receive power from the output coil, and the haptic component may be a movable mass, a magnet, a ferromagnetic element, or any other suitable component or material

Methodology Applied
Scientific EffectElectromagnetic force: Lorentz Force

Data Source

PatentEP4320501B1Active stylus with moveable magnet and inductive charging coil
Publication Date: 2025.11.12 MICROSOFT TECHNOLOGY LICENSING LLC
  • EP4320501B1 patent drawingFigure 1
  • EP4320501B1 patent drawingFigure 2A~2B
  • EP4320501B1 patent drawingFigure 3A~3B

AI summary

An active stylus includes an elongate housing having a tip end and a secondary end, opposite the tip end. An inductive charging coil is mounted within the elongate housing, between the tip end and the secondary end. A magnet configured to magnetically hold the inductive charging coil in a charging position and orientation relative to an inductive charger is moveably mounted within the elongate housing between the tip end and the inductive charging coil.