| 摘要 |
PROBLEM TO BE SOLVED: To further the size/thickness reduction of a speaker to be used as a receiver of a mobile phone or the like. SOLUTION: The speaker holds a circular externally magnetic type magnetic circuit 8 and a diaphragm 13 with a circular voice coil 14 driven by the circuit fixed thereto in a rectangular frame 1. The magnetic circuit 8 comprises a yoke 9 in which a rectangular flange 9b is provided at one edge of a circular center pole 9a, a plate-shaped magnet 10 that has a circular center hole 10a and a rectangular shape nearly same as a flange arranged around the center pole with an annular gap, and an annular pole piece 11 that has the inner diameter nearly same as that of the center hole and the outer diameter nearly same as that of the dimensions of the magnet in a short side direction and holds the magnet with the flange, and a circular magnetic gap 12 into which a voice coil is inserted between the outer circumferential surface of the center pole and the inner circumferential surface of the pole piece is formed. The magnet is divided into two at its central part in a longitudinal direction. COPYRIGHT: (C)2005,JPO&NCIPI
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