Ferrofluid Suspension for Loudspeaker Air Gap Sealing
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Solution Overview
Problem
Conventional moving coil electrodynamic loudspeakers with mechanical suspensions face limitations in terms of structural simplicity and performance efficiency, particularly in achieving effective sealing and magnetic field confinement for ferrofluid-based suspension systems.
Innovation Solution
The implementation of a ferrofluid suspension system where the ferrofluid completely fills the air gap on the mandrel, providing both sealing and magnetic field confinement, along with additional fluidic return/braking mechanisms such as tapered ends and collars to manage excursions and maintain ferrofluid within the gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferrofluid is used to completely fill the air gap for sealing and magnetic field confinement, then sealing efficiency and magnetic field confinement are improved, but the device complexity increases due to additional fluidic return/braking mechanisms
Solution Approach 1:
The ferrofluid suspension system performs multiple functions automatically: it provides sealing between the voice coil assembly and magnet assembly, confines the magnetic field within the air gap, and enables fluidic return/braking through its own presence in the tapered regions. The system uses the ferrofluid's inherent properties rather than adding separate mechanical components for each function.
Solution Approach 2:
The ferrofluid serves multiple purposes simultaneously: it acts as a sealant, a magnetic field confining medium, and a fluidic braking agent. This multi-functionality reduces the need for separate components and simplifies the overall device structure despite the advanced functionality provided.
2Reliability
If ferrofluid completely fills the air gap, then magnetic field confinement is improved, but the volume available for coil movement is reduced
Solution Approach 1:
The air gap region is segmented into different functional zones: the central region where the voice coil moves freely with maximum excursion, and the peripheral/tapered regions where ferrofluid provides confinement and braking. This segmentation allows the magnetic field to be confined where needed while preserving movement volume where required.
Solution Approach 2:
The ferrofluid is contained within the air gap through the tapered geometry of the voice coil assembly, which creates a three-dimensional configuration. The tapering provides vertical confinement of the ferrofluid while maintaining horizontal movement space for the voice coil, effectively using dimensional arrangement to resolve the volume conflict.
3Reliability
If fluidic return/braking mechanisms are added to control ferrofluid during excursions, then ferrofluid retention is improved, but the manufacturing complexity increases
Solution Approach 1:
The fluidic return/braking function is merged with the structural components of the voice coil assembly. The tapered regions of the voice coil former and magnet assembly serve dual purposes: providing mechanical support and creating the geometric constraints necessary for ferrofluid retention during coil excursions.
Solution Approach 2:
The tapered geometry of the voice coil assembly creates variable cross-sectional areas along the vertical axis. This parameter change in the geometric configuration naturally guides the ferrofluid during coil excursions and provides return/braking forces without requiring additional active control mechanisms.
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 enhances the sealing efficiency, reduces mechanical complexity, and allows for larger excursions in compact designs, improving the performance of loudspeakers by maintaining ferrofluid within the air gap and controlling movement effectively.
Implementation Method 1
the ferrofluid completely fills the air gap on the mandrel, providing both sealing and magnetic field confinement
Implementation Method 2
the ferrofluid tends to be placed where the magnetic field and/or the variation of the magnetic field are the highest
Implementation Method 3
said fluidic return/braking means causing a preferably progressive reduction of the space in which the ferrofluid can be placed during excursions of the moving assembly out of its position of equilibrium
Implementation Method 4
When a variable current passes through it, the coil moves in the magnetic field which is generated by a permanent magnet type magnetic field generator
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The invention relates to an electrodynamic transducer (1) with a membrane (2) including an electrodynamic motor in a carcass (7) and in which a coil (6) held by a mandrel (3) connected to the membrane is capable of movement, the mandrel having a shape generated by an essentially linear generatrix, the coil being arranged in an air gap of a vertical free space where it is capable of movement and defined, towards the centre of the transducer, by an inner magnetic structure (4) and, towards the periphery of the transducer, by an outer magnetic structure (5), at least one of the magnetic structures generating a static magnetic field, wherein the transducer does not include any peripheral nor inner suspension and the guiding of the mobile equipment and the pneumatic tightness between the front and rear faces of the membrane being ensured by a ferrofluid. The transducer is characterised in that the mandrel is maintained in the air gap by the ferrofluid applied on at least one of the two faces of the mandrel and entirely filling the air gap. Fluidic return/braking and ferrofluid-retaining means can also be used. The motor can be a Foucault-current one.