| 摘要 |
PURPOSE:To increase a sound pressure level and to improve the size precision of a permanent magnet by providing the iron core of an electromagnet so that the iron core surrounds the permanent magnet in an acoustic transducer equipped with the electromagnet and permanent magnet. CONSTITUTION:An iron core 3 is formed cylindrically and then wound with a coil 2 to constitute an electromagnet, and a columnar permanent magnet 5 is inserted into the internal-diameter part 3a of the iron core 3. Consequently, the magnet 5 is separated from an external cylindrical body 1, which can be made of a magnetic material. Consequently, a magnetic path for magnetic flux generated by the electromagnet is consistuted, as shown in the figure, by a supporting plate 4 of a magnetic material, the external cylindrical body 1, a diaphragm 6, and the iron core 3 to improve its magnetic efficiency while lowering a sound pressure level. Further, the magnet 5 is formed in a simple columnar shape, so the permanent magnet 5 has less errors in forming and baking and high size precision. |
