| 摘要 |
PURPOSE:To prevent magnetic fluid from being scattered by arranging a magnet between two plates, filling in magnetic fluid in a gap formed by a center pole of one plate and a center hole of the other plate and providing a vent hole. CONSTITUTION:The plate 2 having the center pole 8 and the plate 1 having the center hole 9 are fixed by sandwiching an annular manget 3. The magnetic fluid 4 is filled in the gap formed by the center pole 8 and the center hole 9. The change in air pressure due to the temperature change at a space 10 formed at the inside is prevented by forming the vent holes 5-7 to the plates 1, 2. Thus, the magnetic fluid 4 is prevented from being scattered and effective cooling is attained so as to prevent the temperature rise of a voice coil even at a large input. |
