Vibration motor

1. A vibration motor comprising:

a housing having one open surface;

a permanent magnet disposed in an internal space of the housing and interacting with a coil to generate electromagnetic force;

an elastic member formed in the housing;

a mass member coupled to the elastic member to perform resonant movement through the electromagnetic force;

a cover covering the one open surface of the housing; and

an extension part extended from the one open surface of the housing in a height direction thereof and compressed with the cover to closely attach the housing and the cover to each other,

wherein the extension part is compressed with the cover by curling.

2. The vibration motor of claim 1 , wherein the extension part is continuously protruded along an edge of the one open surface of the housing.

3. The vibration motor of claim 1 , wherein the housing has a step supporting the cover.

4. The vibration motor of claim 1 , wherein the extension part has a relatively smaller thickness than that of the housing so as to be easily compressed with the cover.

5. The vibration motor of claim 1 , wherein a height h of the extension part satisfies the following Equation 1:

0.13< h−T 2 <0.50  Equation 1

where T 2 indicates a thickness of the cover.

6. The vibration motor of claim 1 , wherein the housing is formed of stainless steel or a cold rolled steel sheet.

7. The vibration motor of claim 1 , wherein the cover has an inclined surface contacting an end portion of the extension part in a state in which the cover is coupled to the housing.

8. The vibration motor of claim 1 , wherein the cover includes a protrusion part protruded in a radial direction.

9. The vibration motor of claim 8 , wherein the housing has a groove into which the protrusion part is fitted.

10. A vibration motor comprising:

a housing having one open surface;

a permanent magnet disposed in an internal space of the housing and interacting with a coil to generate electromagnetic force;

a cover covering the one open surface of the housing;

an elastic member formed on the cover;

a mass member coupled to the elastic member to perform resonant movement through the electromagnetic force; and

an extension part extended from the one open surface of the housing in a height direction thereof and compressed with the cover to closely attach the housing and the cover to each other,

wherein the extension wart is compressed with the cover by curling.

11. The vibration motor of claim 10 , wherein the extension part is continuously protruded along an edge of the one open surface of the housing.

12. The vibration motor of claim 10 , wherein the housing has a step supporting the cover.

13. The vibration motor of claim 10 , wherein the extension part has a relatively smaller thickness than that of the housing so as to be easily compressed with the cover.

14. The vibration motor of claim 10 , wherein a height h of the extension part satisfies the following Equation 1:

0.13 <h−T 2<0.50  Equation 1

where T 2 indicates a thickness of the cover.

15. The vibration motor of claim 10 , wherein the housing is formed of, stainless steel or a cold rolled steel sheet.

16. The vibration motor of claim 10 , wherein the cover has an inclined surface contacting an end portion of the extension part in a state in which the cover is coupled to the housing.

17. The vibration motor of claim 10 , wherein the cover includes a protrusion part protruded in a radial direction.

18. The vibration motor of claim 17 , wherein the housing has a groove into which the protrusion part is fitted.