Speaker Magnetic Fluid Stability via Flux Density Gradients

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Solution Overview

Problem

Speaker devices with magnetic fluid in the magnetic gap face issues of reduced acoustic conversion efficiency and poor sound quality due to magnetic fluid flying off during coil bobbin movement, causing instability and abnormal noise.

Innovation Solution

A speaker device design featuring a ring-shaped magnet, yoke, plate, and cylindrical coil bobbin with a magnetic fluid-filled gap, where magnetic gradients are formed to maintain the fluid in place by varying magnetic flux density in both circumferential and axial directions, preventing fluid agitation and ensuring stable movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If magnetic fluid is filled in the magnetic gap to reduce weight and improve acoustic conversion efficiency, then acoustic conversion efficiency is improved, but the magnetic fluid flies off during coil bobbin movement causing instability and reduced sound quality

Engineering Contradiction:

Improveacoustic conversion efficiencyVSAvoidstability of magnetic fluid

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces magnetic flux change sections at specific locations (inner circumferential surface of plate and outer circumferential surface of center pole portion) to create localized magnetic flux density variations. These sections generate magnetic forces that selectively hold the magnetic fluid in the magnetic gap without requiring a damper structure, thus maintaining stability while preserving acoustic conversion efficiency.

Inventive Principle:

Principle #3Local quality

2Productivity

If magnetic fluid is filled in the magnetic gap, then weight is reduced and acoustic conversion efficiency is improved, but magnetic fluid agitation produces abnormal noise and poor sound quality

Engineering Contradiction:

Improveacoustic conversion efficiencyVSAvoidabnormal noise

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

By positioning magnetic flux change sections at specific locations (inner circumferential surface of plate and outer circumferential surface of center pole portion), the patent creates localized magnetic fields that stabilize the magnetic fluid in the magnetic gap. This prevents fluid agitation and abnormal noise generation while maintaining the weight reduction and acoustic conversion efficiency benefits.

Inventive Principle:

Principle #3Local quality

3Reliability

If a damper is used to hold the voice coil in the magnetic gap, then stability is improved, but the speaker device becomes heavy and acoustic conversion efficiency is reduced

Engineering Contradiction:

Improvestability of voice coil positioningVSAvoidweight of speaker device

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent replaces the mechanical damper system with a magnetic field-based solution. Magnetic flux change sections generate magnetic forces that hold the voice coil in the magnetic gap without physical contact, eliminating the need for a heavy damper structure while maintaining stability and improving acoustic conversion efficiency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Inventive Principle:

Principle #3Local quality

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 design enhances acoustic conversion efficiency and sound quality by preventing magnetic fluid from flying off and reducing noise, allowing for improved movement of the coil bobbin and better sound reproduction.

Implementation Method 1

A magnetic gradient is formed that is adapted to change the magnetic force acting on the magnetic fluid by changing the magnetic flux density in the circumferential direction of the center pole portion

Methodology Applied

Scientific EffectMagnetic force: Magnetism

Implementation Method 2

A magnetic gradient is formed that is adapted to change the magnetic force acting on the magnetic fluid by changing the magnetic flux density in the axial direction of the center pole portion

Methodology Applied

Scientific EffectMagnetic flux density variation: Magnetic Field

Data Source

PatentUS9462392B2Speaker device with a magnetic gap filled with magnetic fluid and changing magnetic flux density in axial and circumferential directions

Publication Date: 2016.10.04 SONY GROUP CORP

AI summary

A speaker device including a magnet formed in a ring shape; a yoke having a center pole portion inserted in the center of the magnet; a plate formed in a ring shape and arranged on an outer circumferential surface of the center pole portion of the yoke while being attached to the magnet; a coil bobbin formed in a cylindrical shape and movable in the axial direction of the center pole portion while being partially fitted on the center pole portion of the yoke; a voice coil wrapped around the outer circumferential surface of the coil bobbin, at least part of the voice coil being arranged in a magnetic gap formed between the plate and the center pole portion of the yoke; a diaphragm having its inner circumferential portion connected to the coil bobbin; and a magnetic fluid filled in the magnetic gap.