Loudspeaker and mobile device incorporating same
A loudspeaker includes a diaphragm, a voice coil body, and a magnetic circuit. The diaphragm has a first side, which is the surface of a recess defined by a thin part and a thick part formed around the thin part. The voice coil body includes a bobbin and a voice coil. The bobbin has a first end connected to the thin part on the first side of the diaphragm and a second end opposite to the first end. The magnetic circuit has an inner part, an outer part, and a magnetic gap. Part of the magnetic circuit including the first side of the inner part is located from the second end of the bobbin into the bobbin, and the first side of the inner part and the first side of the outer part are located in the recess so that the voice coil is located in the magnetic gap.
1. A loudspeaker comprising:
a frame having a hollow;
a diaphragm located in the hollow of the frame and having:
a first side as a surface of a recess defined by a thin part and a thick part formed around the thin part; and
a second side opposite to the first side;
a first edge connecting an outer peripheral end of the diaphragm and the frame;
a second edge connecting the outer peripheral end of the diaphragm and the frame, the second edge being opposite to the first edge with respect to a center in a thickness direction of the thick part;
a voice coil body including:
a cylindrical bobbin having a first end connected to the thin part on the first side of the diaphragm and a second end opposite to the first end; and
a voice coil wound around at least part of the bobbin; and
a magnetic circuit including:
an inner part; and
an outer part formed around the inner part with a magnetic gap therebetween, wherein part of the magnetic circuit including a first side of the inner part is located from the second end of the bobbin into the bobbin, and the first side of the inner part and a first side of the outer part are located in the recess so that the voice coil is located in the magnetic gap.
2. The loudspeaker of claim 1 , wherein the outer part of the magnetic circuit has a tapered part tapering toward the diaphragm.
3. The loudspeaker of claim 1 , wherein the diaphragm has an inclined surface such that the diaphragm gradually increases in thickness from the thin part toward the thick part.
4. The loudspeaker of claim 3 , wherein the outer part of the magnetic circuit has a tapered part tapering toward the diaphragm, the tapered part being located facing the inclined surface.
5. The loudspeaker of claim 1 , wherein the first edge and the second edge are located symmetrically with respect to a plane perpendicular to a vibration direction of the diaphragm.
6. The loudspeaker of claim 1 , wherein the second side of the diaphragm is flat.
7. The loudspeaker of claim 1 , wherein the diaphragm is made of foamed resin and has a reinforcement layer on at least one of the first side and the second side of the diaphragm.
8. The loudspeaker of claim 1 , further comprising:
a terminal fixed to the frame and located between the first edge and the second edge; and
a connecting wire connecting the terminal and the voice coil.
9. The loudspeaker of claim 1 , further comprising a pedestal fixing the magnetic circuit to the frame.
10. The loudspeaker of claim 9 , wherein the pedestal has an opening.
11. The loudspeaker of claim 1 , wherein the magnetic circuit includes:
a magnet;
a top plate placed on a first side of the magnet;
a bottom plate placed on a second side of the magnet opposite to the first side and magnetically connected to the magnet; and
a yoke placed around the top plate and facing the top plate with the magnetic gap therebetween, the yoke being magnetically connected to the magnet via the bottom plate,
wherein
the inner part of the magnetic circuit is composed of the magnet and the top plate; and
the outer part of the magnetic circuit is composed of the yoke.
12. The loudspeaker of claim 11 , wherein the bottom plate has an opening.
13. The loudspeaker of claim 1 , wherein the magnetic circuit includes:
a ring-shaped magnet;
a ring-shaped top plate placed on a first side of the magnet;
a bottom plate placed on a second side of the magnet opposite to the first side and magnetically connected to the magnet; and
a center pole located in the magnet and facing the magnet with the magnetic gap therebetween, the center pole projecting from the bottom plate,
wherein
the inner part of the magnetic circuit is composed of the center pole; and
the outer part of the magnetic circuit is composed of the magnet and the top plate.
14. The loudspeaker of claim 1 , wherein the magnetic circuit includes:
a first magnet;
a first top plate placed on a first side of the first magnet;
a bottom plate placed on a second side of the first magnet opposite to the first side and magnetically connected to the first magnet;
a second magnet placed around the first magnet and facing the first magnet with the magnetic gap therebetween; and
a second top plate placed on a first side of the second magnet and around the first top plate, the second top plate facing the first top plate with the magnetic gap therebetween,
wherein
the inner part of the magnetic circuit is composed of the first magnet and the first top plate; and
the outer part of the magnetic circuit is composed of the second magnet and the second top plate.
15. A mobile device comprising:
a body;
a drive part mounted in the body;
an amplifier mounted in the body; and
the loudspeaker of claim 1 receiving an output of the amplifier.
16. The mobile device of claim 15 , wherein
the body includes:
an interior part; and
an exterior part covering an outer periphery of the interior part with a predetermined space from the interior part, and
the loudspeaker is located in the space.
17. The mobile device of claim 16 , wherein the exterior part is either a door or a roof.