Asymmetric Magnetic Circuit for Miniature Transducer Width Reduction
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Solution Overview
Problem
Miniature electro-acoustic transducers face challenges in reducing dimensions while maintaining acoustical performance and thermal conditions, as reducing the size of outer magnets weakens the motor and leads to thermal issues.
Innovation Solution
An asymmetric magnetic circuit is employed, where magnetic flux in one air gap is generated by two magnets and in another by a single magnet, allowing for the omission of outer magnets and maintaining equal flux densities, thus reducing the transducer's width without compromising strength or thermal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the width of the miniature transducer is reduced by omitting outer magnets, then the transducer dimensions are reduced, but the motor strength becomes significantly weaker
Solution Approach 1:
The patent applies asymmetry by configuring different air gaps with different magnetic flux generation methods. One air gap has flux generated by two magnets (inner and outer), while the other air gap has flux generated by a single magnet (inner only). This asymmetric configuration allows the transducer to maintain sufficient motor strength in the critical direction while reducing the overall width by omitting outer magnets in certain regions.
Solution Approach 2:
The patent implements local quality by providing different magnetic flux densities in different regions of the air gap. The first air gap portion has flux generated by both inner and outer magnets, while the second air gap portion has flux generated only by the inner magnet. This localized differentiation allows the transducer to maintain strong motor performance where needed while reducing dimensions where outer magnets would increase width.
2Volume of moving object
If the dimensions of outer magnets and diaphragm suspension are reduced, then the transducer width is reduced, but thermal problems occur in the voice coil
Solution Approach 1:
The asymmetric magnetic circuit configuration allows for optimized thermal management by creating different flux paths that can be designed with different thermal characteristics. The air gap portions can be dimensioned differently to optimize both magnetic performance and thermal dissipation paths for the voice coil, preventing thermal buildup while maintaining compact dimensions.
3Volume of moving object
If outer magnets are omitted to reduce width, then the transducer becomes more compact, but the magnetic flux density in air gaps becomes unequal
Solution Approach 1:
The patent applies local quality by creating different magnetic flux generation configurations in different air gap portions. The first air gap has flux from two magnets while the second air gap has flux from one magnet, allowing local optimization of flux density to match the specific requirements of each region while maintaining overall transducer compactness.
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 solution enables a miniature transducer with a small width, strong motor, and optimal thermal conditions, meeting the demands for compact and high-performance loudspeakers in future mobile devices.
Implementation Method 1
the magnetic flux in the first air gap is generated by two magnetic means, such as two permanent magnets in combination. These two magnets may be a common inner magnet in combination with a first outer magnet. Contrary to this, the magnetic flux in the second air gap is primarily generated by a single magnet only, said single magnet being the common inner magnet
Implementation Method 2
The voice coil is arranged in the magnetic gap and fixed to the diaphragm
Data Source
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AI summary
The present invention relates to a miniature electro-acoustic transducer including a magnetic circuit, a diaphragm and a voice coil operatively connected to the diaphragm. The magnetic circuit includes first and second air gap portions adapted to receive first and second voice coil segments, respectively. The magnetic flux acting on the first voice coil segment is provided by inner magnetic means and first outer magnetic means in combination and the magnetic flux acting on the second voice coil segment is essentially provided by the inner magnetic means only.