Horizontal linear vibrator

1. A horizontal linear vibrator comprising:

a cover unit;

a bracket providing an internal space between the cover unit and the bracket;

a vibration unit including a mass body and a yoke part, mounted in the internal space, and making a horizontal, linear movement, the mass body having an insertion part providing an accommodating space in one surface thereof;

a magnetic field unit providing an electromagnetic force to allow the vibration unit to move horizontally; and

one or more sub-mass units inserted in the insertion part in order to adjust a resonance frequency of the vibration unit.

2. The vibrator of claim 1 , wherein the yoke part has an internal space for accommodating the magnetic field therein, and the insertion part is formed at both sides of the internal space.

3. The vibrator of claim 1 , wherein the yoke part has an internal space for accommodating the magnetic field therein, and the insertion part is formed to be separated from the internal space.

4. The vibrator of claim 1 , wherein the insertion part is a hole formed through the mass body.

5. The vibrator of claim 1 , wherein the insertion part is a recess having a shape corresponding to the sub-mass unit.

6. The vibrator of claim 1 , wherein the sub-mass unit is made of tungsten.

7. The vibrator of claim 1 , wherein the yoke part has an internal space for accommodating the magnetic field therein, and the yoke part comprises an extending portion bent to be tightly attached to an outer surface of the mass body.

8. The vibrator of claim 1 , wherein the bracket comprises a bobbin formed in the internal space, and the magnetic field unit comprises a coil part insertedly formed in the bobbin and a magnet disposed to be adjacent to the coil part.

9. The vibrator of claim 8 , wherein the coil part has a quadrangular shape.

10. The vibrator of claim 1 , wherein a circuit board is installed at an upper portion of the bracket and connected with an external input terminal.