PURPOSE: To obtain a large vibration stroke of a diaphragm member by an electric signal of small power by increasing the length of a moving cylinder in an axial direction to increase the vibration stroke of the vibration member.
CONSTITUTION: The induction type speaker consists of a permanent magnet, a yoke 2, a center magnetic pole 3, a moving cylinder 7, a vibration member 6 and a fixed coil 8. The permanent magnet 1 is cylindrical type, both end faces are formed bipolar, magnetic flux is led from both end faces by the yoke 2 and the center magnetic pole 3 to form a radial DC magnetic field between annular gaps 4. The yoke 2 and the center magnetic pole 3 form the annular gap 4. An electric signal from an amplifier or the like flows to the fixed coil 8, an AC magnetic field is generated by this current, an induced electromotive force is produced in the moving cylinder 7, and the moving cylinder 7 is vibrated by the electromagnetic force produced by the current from the induced electromotive force and the DC magnetic field of the annular gap 4. The electric signal is outputted as sound by the vibration member 6 vibrated incorporatedly with the vibration of the moving cylinder 7.
KAGUMA HIDEAKI
SHIBANO MAKOTO
MURAKAMI MITSUO
