Acoustic Transducer Magnetic Circuit With Protective Composite Layer
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Solution Overview
Problem
Existing magnetic circuits in acoustic transducers face issues of surface peeling due to strong magnetic fields and reduced magnetic flux density due to non-magnetic metal coatings on magnetic powder particles, leading to increased eddy currents and current distortion.
Innovation Solution
A magnetic circuit design incorporating a soft magnetic composite material with a protective layer made of a non-magnetic material, such as copper, to suppress peeling and eddy currents, while maintaining magnetic flux density by coating the composite material with a phosphoric acid-based chemical conversion coating or silicone resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If magnetic powder is coated with resin to suppress eddy currents, then eddy current suppression is improved, but surface peeling occurs due to fragility under strong magnetic fields
Solution Approach 1:
The patent uses a composite material structure consisting of magnetic powder particles coated with resin, forming a soft magnetic composite material. This composite structure allows the material to simultaneously exhibit magnetic properties from the iron powder and eddy current suppression from the resin coating, while the compression molding process creates a unified structure that resists surface peeling under magnetic field stress
2Object-generated harmful factors
If magnetic powder particles are coated with non-magnetic metal to reduce current distortion, then current distortion is reduced, but magnetic flux density decreases due to increased proportion of non-magnetic metal
Solution Approach 1:
The patent changes the material parameters by selecting resin with specific electrical insulation properties and magnetic powder with optimized particle size and magnetic properties. By controlling the coating thickness and composition, the material achieves both eddy current suppression and maintained magnetic flux density, resolving the contradiction between reducing current distortion and maintaining magnetic strength
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 effectively reduces surface peeling and eddy currents, enhancing acoustic performance by minimizing distortion and improving sound pressure in the high-frequency domain.
Implementation Method 1
the occurrence of eddy currents in the magnetic circuit is suppressed by using, as a magnetic material used in the magnetic circuit, a soft magnetic composite material formed by coating and insulating the surface of a ferromagnetic powder
Implementation Method 2
the surface thereof may peel due to a strong magnetic field generated in the magnetic gap
Data Source
AI summary
An object of the present invention is to provide a magnetic circuit for an acoustic transducer, the magnetic circuit enabling peeling of the surface of a member formed by compression-molding a soft magnetic composite material to be suppressed. The present invention is a magnetic circuit for an acoustic transducer, the magnetic circuit including: a yoke 151; a magnet 152; and a top plate 153, wherein the yoke 151 includes a bottom surface portion 151a and a pole piece 151b provided perpendicular to the bottom surface portion 151a, the magnet 152 and the top plate 153 are provided in that order on the bottom surface portion 151a, a magnetic gap 141 in which a voice coil 14 is disposed is formed between the pole piece 151b and the top plate 153, at least one of the pole piece 151b and the top plate 153 includes: a composite material part 154 in a position facing the magnetic gap 141; and a protective layer 155 covering at least a surface of the composite material part 154, the composite material part 154 is formed from a soft magnetic composite material, and the material of the protective layer 155 differs from the soft magnetic composite material.