| 摘要 |
PROBLEM TO BE SOLVED: To miniaturize more an electroacoustic transducer excellent in acoustic characteristics. SOLUTION: The electroacoustic transducer includes: an inner magnetic type magnetic circuit 2 composed of a planar magnet 4 and a top plate 5 successively layered on the upper part of a yoke 3; a voice coil 7 disposed inside a magnetic gap 6 formed between the side wall of the yoke 3 and the top plate 5; a diaphragm 9 for holding the voice coil 7; and a frame 1 in a rectangular shape for holding the inner magnetic type magnetic circuit 2 and the diaphragm 9. A ventilation part 8 passing through from an upper surface to a lower surface at the center part of the top plate 5, the magnet 4, and the yoke 3 is formed. The ventilation part 8 formed at the magnet 4 constituting the inner magnetic type magnetic circuit 2 is a ventilation hole 4a disposed at the center part of the planar magnet 4 or a ventilation slit (4b) in which end faces of two planar magnets (4A and 4B) are disposed facing each other and which is set to a desired clearance t. The size in the width direction of the magnet can be set regardless of the size of a hole diameter. COPYRIGHT: (C)2008,JPO&INPIT
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