Sound production device
An armature is vibrated by a magnetic field generating unit and a coil. A diaphragm is driven by the armature. In the magnetic field generating unit, a first protective layer is provided on the magnetized surface of a first magnet, and a second protective layer is provided on the magnetized surface of a second magnet. Since protective layers with a certain thickness are present, it is possible to prevent the armature from being left attracted to the first magnet or second magnet.
1. A sound production device comprising:
an armature made of a magnetic material, the armature having first and second plates and vibrating in a plate thickness direction with a bottom of the armature supported;
a driving mechanism configured to vibrate the armature; and
a diaphragm vibrated by the armature; wherein
the driving mechanism has a first magnet facing a first surface of the armature, a second magnet facing a second surface of the armature, and a yoke configured to hold the first magnet and a second yoke,
the armature has a free end coupled to the diaphragm via a transmission body, and
a magnetized surface of the first magnet, the magnetized surface facing the armature, and a magnetized surface of the second magnet, the magnetized surface facing the armature, have different magnetic poles, a non-magnetic protective layer that has a width that is larger than a width of the armature and formed on at least a top edge of the free end of each armature on at least part of each of the magnetized surfaces.
2. The sound production device according to claim 1 , wherein:
the armature is capable of maintaining a neutral attitude distant from the two magnetized surfaces with an elastic force of the armature itself; and
a thickness of the protective layers is determined so that when the armature comes into contact with either of the protective layers, a force with which the armature returns to the neutral position with the elastic force is larger than a force with which the magnet attracts the armature.
3. The sound production device according to claim 1 , wherein each magnetized surface has a top edge facing the free end of the armature and a rear edge facing the bottom side of the armature, the protective layers being disposed within a predetermined range starting from the top edge in a backward direction.
4. The sound production device according to claim 1 , wherein the protective layer is a resin layer.
5. The sound production device according to claim 1 , wherein the protective layer provided on the magnetized surface of the first magnet and the protective layer provided on the magnetized surface of the second magnet are colored in different hues.
6. The sound production device according to claim 1 , wherein the protective layers are formed in a whole region from a top edge to a rear edge of the magnetized surfaces.