Magnetic Encoder Layout for Stable Position Signals

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Solution Overview

Problem

Existing encoder devices using magnetic wires face challenges in generating stable electric signals due to unnecessary magnetic fields, which affects the reliability of position detection, particularly in noisy environments.

Innovation Solution

The encoder device incorporates a magnetosensitive part with a specific magnetic characteristic that changes with the magnetic field, disposed orthogonal to the magnet's side surface, generating electric signals based on the magnetic field changes associated with relative movement, thereby reducing noise interference and enhancing signal stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a magnetic wire is used to detect position information, then the encoder device can obtain rotating speed and position, but the unnecessary magnetic field of the magnet causes noises that reduce signal stability

Engineering Contradiction:

Improveposition detection precisionVSAvoidsignal stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The magnetosensitive part is configured with a specific orientation where its length direction is orthogonal to the tangential directions of magnetic field lines. This local quality optimization ensures that the part responds selectively to radial magnetic field components while ignoring tangential components, thereby improving signal stability without sacrificing detection precision

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The encoder device uses a composite structure combining a magnet with specific polarity arrangement and a magnetosensitive part with optimized magnetic characteristics. This composite configuration enables the system to generate stable electric signals by leveraging the interaction between the magnet's radial field and the magnetosensitive part's orientation

Inventive Principle:

Principle #40Composite materials

2Measurement precision

If the magnetosensitive part is placed close to the magnet to improve detection sensitivity, then position detection precision improves, but the impact of unnecessary magnetic field components increases

Engineering Contradiction:

Improvedetection sensitivityVSAvoidnoise from unnecessary magnetic field

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention converts the harmful effect of unnecessary magnetic field components into a beneficial selective detection mechanism. By orienting the magnetosensitive part orthogonally to tangential field lines, the device naturally filters out unwanted magnetic field components while maintaining sensitivity to the desired radial field components

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 effectively generates high-output, stable electric signals by minimizing the impact of unnecessary magnetic field components, improving the reliability of position detection and reducing maintenance needs for the encoder device.

Implementation Method 1

a magnet having a plurality of polarities along a moving direction of the moving part; and an electric signal generation unit for generating an electric signal, based on a magnetic characteristic of a magnetosensitive part, the electric signal generation unit having the magnetosensitive part whose magnetic characteristic is changed by a change in magnetic field associated with relative movement to the magnet

Methodology Applied

Scientific EffectMagnetic field change: Magnetic Field

Data Source

PatentUS11858132B2Encoder device, drive device, stage device, and robot device

Publication Date: 2024.01.02 NIKON CORP

AI summary

An encoder device including a position detection unit for detecting position information of a moving part; a magnet having a plurality of polarities along a moving direction of the moving part; and an electric signal generation unit for generating an electric signal, based on a magnetic characteristic of a magnetosensitive part, the electric signal generation unit having the magnetosensitive part whose magnetic characteristic is changed by a change in magnetic field associated with relative movement to the magnet, wherein the magnetosensitive part is disposed so that the magnetosensitive part is spaced apart from a side surface of the magnet in a direction orthogonal to the moving direction and a length direction of the magnetosensitive part is orthogonal to tangential directions of at least some of magnetic field lines of the magnet.