Dual magnetic structure of vibration speaker

Disclosed is a multifunction actuator comprising: a case having an internal space; a sound generating diaphragm with the outer end fixed to the upper end of the case; a voice coil cylindrically wound and fixed around the lower end of the diaphragm; a main magnet magnetized in the upward and downward directions; an upper plate attached to the magnet for forming a magnetic circuit; a yoke for forming the magnetic circuit with the magnet; a weight for forming a vibrating body with the upper plate and the yoke; suspension springs for supporting the weight from the upside and downside; a vibrating coil installed in the lower end of the case for generating vibration by using a portion of magnetic flux generated as above; and a ring-shaped auxiliary magnet installed in the yoke; wherein the magnetic circuit is provided to increase strength of magnetic flux under the same pressure while defining the same magnetic field as previous one so that sound pressure and vibration features of the multifunction actuator of the vibration speaker used in the mobile communication terminals such as the cellular phone, the pager and the like can be enhanced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to adding a ring-shaped auxiliary magnet in a yoke region, by which magnetic force is also generated in the peripheral ring-shaped magnet while magnetic force was generated only in a cylindrical magnet at a central portion in the prior art, thereby increasing magnet volume for generating magnetic force. Hereinafter describing in detail about a multifunction actuator according to the first embodiment of the invention, the actuator comprises a case 28 having an internal space, a sound generating diaphragm 21 with the outer end fixed at the upper end of the case 28 , a voice coil 22 cylindrically wound and fixed around the lower end of the diaphragm 21 , a main magnet 24 contained within the case 28 and magnetized in the upward and downward directions, an upper plate 23 attached to the main magnet 24 for forming a magnetic circuit, a yoke 25 for forming a magnetic circuit with those components, a weight 26 for composing a vibrating body with the upper plate 23 and the yoke 25 , suspension springs 27 and 29 for supporting the weight 26 from the upside and downside thereof, a vibrating coil 30 installed in the lower end of the case for generating vibration by using a portion of magnetic flux generated in such a manner, and a ring-shaped auxiliary magnet 31 installed in the yoke 25 . In the multifunction actuator like this, when an AC current is externally applied in general, magnetic field is generated in the voice coil 22 in the magnetic circuit composed of the upper plate 23 , the magnet 24 and the yoke 25 , in which distribution of magnetic lines of force can be indicated as shown in FIG. 5 . As shown in FIG. 5 , the magnetic lines of force from the N pole of the main magnet 24 proceed to the S pole of the main magnet 24 through the upper plate 23 , the voice coil 22 , the yoke 25 upper part, the auxiliary magnet 31 and the yoke 25 lower part in sequence to form magnetic field, in which the voice coil 22 functions as a speaker by using magnetic flux due to the above magnetic circuit. Meanwhile, the vibrating coil 30 generates magnetic force by using a portion of magnetic flux leaks downward as the magnetic lines of force as shown in FIG. 5 at the lower end of the yoke 25 , in which the whole volume of the magnet can be increased if the auxiliary magnet 31 is used. Therefore, the vibrating coil 30 can be supplied with sufficient strength of magnetic flux differently from the structure of the prior art. Here, it is required that the auxiliary magnet 31 is shaped as a ring and has pole directions oriented differently from those of the main magnets 24 so that the directions of the magnetic lines of force may not be changed. As described above, the invention is characterized in that the magnetic circuit maintains similar to that of the prior art and at the same time can increase the amount of magnetic flux leaking downward so that a sufficient amount of magnetic flux can be supplied to generate electromagnetic force to the vibrating coil. Here, output sound pressure is raised 2 to 3 dB on the average and vibration performance shows the enhancement of about 15% in the case of using the auxiliary magnet disclosed in the invention. The multifunction actuator structure using dual magnets can be realized in various forms, in which the second embodiment of the invention can be represented as in FIG. 6 . A multifunction actuator according to the second embodiment comprises a case 208 having an internal space, a sound generating diaphragm 201 with the outer end fixed to the upper end of the case 208 , a voice coil 202 cylindrically wound and fixed around the lower end of the diaphragm 201 , a main magnet 204 magnetized in the upward and downward directions, an upper plate 203 attached to the magnet 204 for forming a magnetic circuit, a yoke 205 for forming the magnetic circuit with the magnet 204 , a weight 206 for forming a vibrating body with the upper plate 203 and the yoke 205 , suspension springs 207 and 209 for supporting the weight 206 from the upside and downside thereof, and a ring-shaped auxiliary magnet 210 installed in the yoke 205 . The third embodiment of the invention can be represented as in FIG. 7 . A multifunction actuator according to the third embodiment of the invention comprises a case 308 having an internal space, a main magnet 304 magnetized in the upward and downward directions, an upper plate 303 attached to the magnet for forming a magnetic circuit, a yoke 305 for forming the magnetic circuit with the magnet 304 , a weight 306 for forming a vibrating body with the upper plate 303 and the yoke 305 , suspension springs 307 and 309 supporting the weight 306 from the upside and downside thereof, a sound generating diaphragm 301 directly connected to one end of the weight 306 , a voice coil 302 cylindrically wound and fixed around the lower end of the diaphragm 301 , a vibrating coil 320 installed in the lower end of the case 308 for generating vibration by using a portion of magnetic flux generated in such a manner, and a ring-shaped auxiliary magnet 310 installed in the vibrating coil 320 and the yoke 305 . The operative principles of the second and third embodiments of the invention are similar to that of the first embodiment of the invention and therefore the explanation thereof will be omitted. Also, the dual magnet structure of the invention can be variously applied to a micro speaker with a magnetic circuit block having a similar structure to that of the multifunction actuator thereby permitting a very large area of application. FIG. 8 shows a micro speaker employing the dual magnet structure. The micro speaker generally comprises a case 408 having an internal space, a sound generating diaphragm 401 with the outer end fixed to the upper end of the case 408 , a voice coil 402 cylindrically wound and fixed around the lower end of the diaphragm 401 , a main magnet 404 magnetized in the upward and downward directions, an upper plate 403 attached to the magnet 404 for forming a magnetic circuit, and a yoke 405 for forming the magnetic circuit with the magnet 404 , in which an auxiliary magnet 410 of the invention is installed in a ring shape to define a dual magnetic structure. Considering the operative principle, when a high-frequency AC current is externally applied in general to the voice coil 402 in the magnetic circuit composed of the upper plate 403 , the main magnet 404 and the yoke 405 , electromagnetic force is generated for audio output, in which magnetic lines of force from the N pole of the main magnet 404 proceed to the S pole of the main magnet through the upper magnet 403 , the voice coil 402 , the yoke 405 upper part, the auxiliary magnet 410 and the yoke lower part in sequence to form magnetic field. Here, the voice coil 402 functions as a speaker by using magnetic flux due to the magnetic circuit. Here, it is required that the auxiliary magnet 410 is shaped as a ring and has pole directions oriented differently from those of the main magnets 404 so that the directions of the magnetic lines of force may not be changed. It will be clarified that the structures described as above in realizing the invention are only embodiment whereas different forms of apparatuses can be made by those skilled in the art from the scope and the basic principle of the invention recorded in claims of the invention. According to the invention, when magnet volume is increased, magnetic flux flowing through the magnetic circuit is enhanced to raise audio and vibration output even under the same pressure. Also, the principle can be variously applied to speakers which are currently used to have a large area of application.