| 摘要 |
PURPOSE:To realize a high speed response by forming a through hole which is wide at the center and narrowed toward the periphery at the magnetic yoke of a voice coil, thereby reducing the impedance of the coil without reducing a magnetic flux density in a magnetic air gap. CONSTITUTION:A through hole 6 which has a penetrating direction substantially parallel to permanent magnets 3a, 36 and substantially perpendicular with respect to the moving direction designated by an arrow A of a voice coil 1, and is wide at the center and narrowed toward the periphery is formed at a magnetic yoke 2b disposed at the center of the coil 1. Thus, magnetic fluxes generated from the permanent magnets 3a, 3b and guided from magnetic yokes 2a, 2c toward the yoke 2b are substantially saturated. Accordingly, since the magnetic flux generated by a current flowing in the coil 1 is scarcely conducted to reduce the inductance of the coil 1, a high speed response can be realized.
|
