Speaker device, audio visual equipment, mobile information processing apparatus, vehicle, and earphone

1. A speaker device, comprising:

a magnetic circuit including: a plate; a magnet having a surface fixed to one surface of the plate, and having no through-hole; and a yoke fixed to a surface of the magnet opposite to the surface fixed to the plate, the yoke forming a magnetic gap between itself and an outer peripheral surface of the plate;

a voice coil disposed in the magnetic gap;

a diaphragm directly or indirectly fixed to the voice coil;

a supporting part configured to support the diaphragm; and

a magnetic fluid disposed in at least a space between an outer peripheral surface of the voice coil and an inner peripheral surface of the yoke, wherein

a rear surface side space between a rear surface of the diaphragm and a front surface of the plate communicates with a space outside the speaker device through a gap for communication which is formed in at least a part, in a peripheral direction of the voice coil, of a space between the outer peripheral surface of the plate and an inner peripheral surface of the voice coil,

a radius of curvature of a corner portion in the inner peripheral surface of the yoke is 0.5 mm or more,

the voice coil has a shape selected from a circular shape, a track shape, an oval shape, and a shape including a plurality of linear segments and a plurality of curved segments connecting the linear segments with each other, and

a distance between the inner peripheral surface of the voice coil and the outer peripheral surface of the plate is not uniform in the peripheral direction of the voice coil.

2. The speaker device according to claim 1 , wherein

a through-hole is formed in the yoke outside a region where the magnet is fixed to the yoke, and

the rear surface side space communicates with the space outside the speaker device through the gap for communication and the through-hole of the yoke.

3. The speaker device according to claim 1 , wherein

the outer peripheral surface of the plate has a pair of long-side side surfaces opposing each other in a short side direction of the plate, and a pair of short-side side surfaces opposing each other in a long side direction of the plate, and

in the space between the outer peripheral surface of the plate and the inner peripheral surface of the voice coil, the magnetic fluid is disposed outside the long-side side surfaces, and the gap for communication is formed outside at least a part of the short-side side surfaces.

4. The speaker device according to claim 3 , wherein

portions of the inner peripheral surface of the voice coil, opposing the short-side side surfaces, are more distant from the outer peripheral surface of the plate than portions of the inner peripheral surface of the voice coil opposing the long-side side surfaces.

5. The speaker device according to claim 3 , wherein

projections projecting outward are formed at a part of the short-side side surfaces, and

in the space between the outer peripheral surface of the plate and the inner peripheral surface of the voice coil, the magnetic fluid is disposed outside top end surfaces of the projections.

6. The speaker device according to claim 1 , wherein

the gap for communication is a plurality of gaps for communication,

the plate has a planar shape having cutouts at four corners, and

in the space between the outer peripheral surface of the plate and the inner peripheral surface of the voice coil, the cutouts form the gaps for communication, and the magnetic fluid is disposed at portions other than the cutouts.

7. The speaker device according to claim 3 , wherein

the supporting part supports the diaphragm over an entire periphery of the diaphragm.

8. The speaker device according to claim 1 , wherein

the supporting part includes a plurality of supporting members each supporting the diaphragm, and

between the outer peripheral surface of the voice coil and the inner peripheral surface of the yoke, the magnetic fluid is disposed over an entire periphery in the peripheral direction of the voice coil.

9. The speaker device according to claim 2 , wherein

the through-hole is formed in a side surface of an outer peripheral portion of the yoke.

10. The speaker device according to claim 2 , wherein

a lead wire drawn from the voice coil passes through the through-hole.

11. The speaker device according to claim 2 , wherein

the yoke includes a plurality of the through-hole, and

the plurality of the through-holes are arranged at equal angular intervals on a virtual circle concentric with a centroid axis of the voice coil parallel to a vibration direction of the diaphragm.

12. An audio visual equipment including the speaker device according to claim 1 .

13. A mobile information processing apparatus including the speaker device according to claim 1 .

14. A vehicle including the speaker device according to claim 1 .

15. An earphone including the speaker device according to claim 1 .

16. The speaker device according to claim 1 , wherein

the magnetic fluid is disposed only in the space between the outer peripheral surface of the voice coil and the inner peripheral surface of the yoke, and no magnetic fluid is disposed in the space between the outer peripheral surface of the plate and the inner peripheral surface of the voice coil.

17. A speaker device, comprising:

a magnetic circuit including: a plate; a magnet having a surface fixed to one surface of the plate, and having no through-hole; and a yoke fixed to a surface of the magnet opposite to the surface fixed to the plate, the yoke forming a magnetic gap between itself and an outer peripheral surface of the plate;

a voice coil disposed in the magnetic gap;

a diaphragm directly or indirectly fixed to the voice coil;

a supporting part configured to support the diaphragm; and

a magnetic fluid disposed in at least a space between an outer peripheral surface of the voice coil and an inner peripheral surface of the yoke, wherein

a rear surface side space between a rear surface of the diaphragm and a front surface of the plate communicates with a space outside the speaker device through a gap for communication which is formed in at least a part, in a peripheral direction of the voice coil, of a space between the outer peripheral surface of the plate and an inner peripheral surface of the voice coil,

the outer peripheral surface of the plate has a pair of long-side side surfaces opposing each other in a short side direction of the plate, and a pair of short-side side surfaces opposing each other in a long side direction of the plate,

in the space between the outer peripheral surface of the plate and the inner peripheral surface of the voice coil, the magnetic fluid is disposed outside the long-side side surfaces, and the gap for communication is formed outside at least a part of the short-side side surfaces, and

portions of the inner peripheral surface of the voice coil, opposing the short-side side surfaces, are more distant from the outer peripheral surface of the plate than portions of the inner peripheral surface of the voice coil opposing the long-side surfaces.

18. A speaker device, comprising:

a magnetic circuit including: a plate; a magnet having a surface fixed to one surface of the plate, and having no through-hole; and a yoke fixed to a surface of the magnet opposite to the surface fixed to the plate, the yoke forming a magnetic gap between itself and an outer peripheral surface of the plate;

a voice coil disposed in the magnetic gap;

a diaphragm directly or indirectly fixed to the voice coil;

a supporting part configured to support the diaphragm; and

a magnetic fluid, wherein

a rear surface side space between a rear surface of the diaphragm and a front surface of the plate communicates with a space outside the speaker device through a gap for communication which is formed in at least a part, in a peripheral direction of the voice coil, of a space between the outer peripheral surface of the plate and an inner peripheral surface of the voice coil,

the outer peripheral surface of the plate has a pair of long-side side surfaces opposing each other in a short side direction of the plate, and a pair of short-side side surfaces opposing each other in a long side direction of the plate,

in the space between the outer peripheral surface of the plate and the inner peripheral surface of the voice coil, the magnetic fluid is disposed outside the long-side side surfaces, and the gap for communication is formed outside at least a part of the short-side side surfaces,

projections projecting outward are formed at a part of the short-side side surfaces, and

in the space between the outer peripheral surface of the plate and the inner peripheral surface of the voice coil, the magnetic fluid is disposed outside top end surface of the projections.

19. A speaker device, comprising:

a magnetic circuit including: a plate; a magnet having a surface fixed to one surface of the plate, and having no through-hole; and a yoke fixed to a surface of the magnet opposite to the surface fixed to the plate, the yoke forming a magnetic gap between itself and an outer peripheral surface of the plate;

a voice coil disposed in the magnetic gap;

a diaphragm directly or indirectly fixed to the voice coil;

a supporting part configured to support the diaphragm; and

a magnetic fluid, wherein

a rear surface side space between a rear surface of the diaphragm and a front surface of the plate communicates with a space outside the speaker device through gaps for communication which are formed in at least a part, in a peripheral direction of the voice coil, of a space between the outer peripheral surface of the plate and an inner peripheral surface of the voice coil,

the plate has a planar shape with cutouts at four corners, and

in the space between the outer peripheral surface of the plate and the inner peripheral surface of the voice coil, the cutouts form the gaps for communication, and the magnetic fluid is disposed at portions other than the cutouts.