Vibration generating apparatus

1. A vibration generating apparatus comprising:

an elastic member having both end portions thereof fixedly installed on a support part of a lower case;

a piezoelectric element installed on one surface of the elastic member; and

a mass body part disposed above the piezoelectric element to increase an amount of vibrations of the elastic member,

wherein the mass body part is provided with protrusion portions for first contacting the lower case at the time of an external impact,

wherein the mass body part comprises:

a mass body case connected to the piezoelectric element through an adhesive member, the adhesive member being formed of a soft material; and

a mass body installed in the mass body case, and

wherein the protrusion portions are provided on the mass body case.

2. The vibration generating apparatus of claim 1 , wherein the protrusion portions are extended downwardly from both side surfaces of the mass body case, respectively, and are disposed at a central portion of the mass body case in a length direction thereof.

3. The vibration generating apparatus of claim 1 , wherein the protrusion portions are extended downwardly from both side surfaces of the mass body case, respectively, and are disposed so as to be provided adjacently to both end portions thereof of the mass body case in a length direction thereof, respectively.

4. The vibration generating apparatus of claim 2 , wherein distal ends of the protrusion portions are disposed below a damper member installed on a lower surface of the elastic member.

5. The vibration generating apparatus of claim 1 , wherein the adhesive member is formed of tape containing a rubber component.

6. The vibration generating apparatus of claim 1 , wherein the protrusion portion has a polygonal shape when viewed from a front.

7. The vibration generating apparatus of claim 1 , wherein the protrusion portions include first and second protrusions disposed so as to be spaced apart from a center line of the mass body case by a predetermined interval and third and fourth protrusions disposed so as to be spaced apart from the first and second protrusions, respectively, in a length direction.

8. The vibration generating apparatus of claim 7 , wherein the third and fourth protrusions are disposed at both end portions thereof of the mass body case, respectively.

9. The vibration generating apparatus of claim 7 , wherein the first and second protrusions have sizes larger than those of the third and fourth protrusions.

10. The vibration generating apparatus of claim 7 , wherein the mass body case is provided with a groove into which the piezoelectric element is inserted.

11. The vibration generating apparatus of claim 1 , wherein the mass body case is provided with bonding protrusions for increasing coupling force between the mass body case and the mass body, and the mass body is provided with bonding grooves into which the bonding protrusions are inserted.

12. A vibration generating apparatus comprising:

an elastic member having both end portions thereof fixedly installed on a support part of a lower case;

a piezoelectric element installed on one surface of the elastic member;

a mass body case connected to the piezoelectric element through an adhesive member, wherein the adhesive member is formed of a soft material; and

a mass body installed in the mass body case to increase an amount of vibrations of the elastic member,

wherein the mass body case is provided with protrusion portions extended downwardly from both side surfaces of the mass body case, respectively.

13. The vibration generating apparatus of claim 7 , wherein distal ends of the protrusion portions are disposed below a damper member installed on a lower surface of the elastic member.