Speaker device

1. A speaker device comprising:

a magnet having a central axis;

a yoke having a central axis, the central axis of the yoke being identical to the central axis of the magnet, the magnet being attached to the yoke;

a main plate attached to the magnet;

at least one sub-plate attached to the magnet and positioned to be separated from the main plate in an axial direction of the central axis;

a coil bobbin formed in a tubular shape and changeable in the axial direction;

a voice coil wound around an outer circumferential surface of the coil bobbin, at least a portion of the voice coil being disposed in a main magnetic gap formed between the main plate and the yoke;

a vibration plate having an inner circumferential portion connected to the coil bobbin, and vibrating according to a change of the coil bobbin; and

a magnetic fluid filling at least one sub-magnetic gap formed between the sub-plate and the yoke,

wherein,

the coil bobbin includes pluralities of through-holes positioned in the sub-magnetic gap and filled with the magnetic fluid,

at least one of the through-holes is located at a position where the magnetic fluid is present,

the sub-magnetic gap is positioned on a same side of the vibration plate as the main magnetic gap,

a support ring is attached to an inner circumferential portion of the sub-plate,

at least a portion of the support ring is positioned inside the inner circumferential surface of the sub-plate,

a first one of the pluralities of through-holes is separated from a second one of the pluralities of through-holes in a circumferential direction of the coil bobbin, and

positions of through-holes included in the first one of the pluralities of through-holes are shifted in the axial direction relative to positions of through-holes included in the second one of the pluralities of through-holes.

2. The speaker device according to claim 1 , wherein the support ring corresponds to a magnetic substance.

3. The speaker device according to claim 1 , wherein a magnetic gradient is formed to change a magnetic force with respect to the magnetic fluid by changing a magnetic flux density in the axial direction.

4. The speaker device according to claim 1 , wherein a magnetic gradient is formed to change a magnetic force with respect to the magnetic fluid by changing a magnetic flux density in a circumferential direction of the central axis.

5. The speaker device according to claim 4 , wherein a magnetic flux change unit forming the magnetic gradient in the axial direction is provided in the sub-plate or the yoke.

6. The speaker device according to claim 5 , wherein a distal end portion of the yoke is caused to protrude from the sub-plate in the axial direction, and the distal end portion is provided as the magnetic flux change unit.

7. The speaker device according to claim 5 , wherein an inclined plane inclined in the axial direction is formed on a surface of the sub-plate or the yoke, and a portion on which the inclined plane is formed is provided as the magnetic flux change unit.

8. The speaker device according to claim 5 , wherein a curved surface is formed on a surface of the sub-plate or the yoke, and a portion on which the curved surface is formed is provided as the magnetic flux change unit.

9. The speaker device according to claim 4 , wherein a magnetic flux change unit forming the magnetic gradient in the axial direction is provided in the sub-plate and the yoke.

10. The speaker device according to claim 9 , wherein an inclined plane inclined in the axial direction is formed on respective surfaces of the sub-plate and the yoke, and respective portions on which the inclined plane is formed are provided as the magnetic flux change unit.

11. The speaker device according to claim 9 , wherein a curved surface is formed on a surface of the sub-plate or the yoke, and a portion on which the curved surface is formed is provided as the magnetic flux change unit.

12. The speaker device according to claim 1 , wherein the support ring extends into the sub-magnetic gap and contacts the magnetic fluid.

13. The speaker device according to claim 1 , wherein the voice coil is spaced apart from the pluralities of through-holes in the axial direction.

14. A speaker device comprising:

a magnet having a central axis;

a yoke having a central axis, the central axis of the yoke being identical to the central axis of the magnet, the magnet being attached to the yoke;

a main plate attached to the magnet;

at least one sub-plate attached to the magnet and positioned to be separated from the main plate in an axial direction of the central axis;

a coil bobbin formed in a tubular shape and changeable in the axial direction;

a voice coil wound around an outer circumferential surface of the coil bobbin, at least a portion of the voice coil being disposed in a main magnetic gap formed between the main plate and the yoke;

a vibration plate having an inner circumferential portion connected to the coil bobbin, and vibrating according to a change of the coil bobbin; and

a magnetic fluid filling at least one sub-magnetic gap formed between the sub-plate and the yoke,

wherein,

the coil bobbin includes pluralities of through-holes positioned in the sub-magnetic gap and filled with the magnetic fluid,

the voice coil is spaced apart from the pluralities of through-holes in the axial direction,

at least one of the through-holes is located at a position where the magnetic fluid is present,

the sub-magnetic gap is positioned on a same side of the vibration plate as the main magnetic gap,

a support ring is attached to an inner circumferential portion of the sub-plate,

at least a portion of the support ring is positioned inside the inner circumferential surface of the sub-plate,

the through-holes have a slit shape extending in the axial direction of the coil bobbin, and a first of the pluralities of through-holes is formed to be separated from a second of the pluralities of through-holes in a circumferential direction of the coil bobbin, and

positions of the first and second pluralities of through-holes are shifted in the axial direction.