Patent Publication Number: US-9426594-B2

Title: Miniature speaker

Description:
FIELD OF THE INVENTION 
     The present invention relates to electro-acoustic transducers, more particularly to a miniature speaker having a front cover with sufficient strength. 
     DESCRIPTION OF RELATED ART 
     With the rapid development of wireless communication technologies, mobile phones are widely used. Users require mobile phones to not only have voice function, but also have high quality acoustic performance. A mobile phone also provides the user with entertainment contents, such as music, video, game. For converting electrical signals to audible sounds, a speaker is a necessary component used in a mobile phone for generating sounds. As the mobile phone is designed to be smaller and smaller, the speaker used therein is also required to have a low profile with small size. 
     Generally, a miniature speaker related to the present disclosure electrically connects to external circuits via elastic contacts for converting electrical signals to audible sounds. Such a miniature speaker includes a frame, a sound generator accommodated in the frame, and a front cover assembled with the frame for protecting the sound generator. The sound generator includes a membrane and a voice coil connected to the membrane. While electrified, the voice coil activates the membrane to vibrate, thus audible sounds are generated. Typically, the front cover includes a gasket pressing an edge of the membrane for fixing the membrane to the frame, and a top cover mounted on the gasket. As mentioned above, the speaker is designed to be smaller and smaller; each of the gasket and the top cover has a small size and has poor strength. Due to the poor strength of the front cover, the gasket or the top cover is easily to be deformed or even broken during assembling process, which seriously affects the acoustic performance of the miniature speaker. 
     Accordingly, an improved miniature speaker which can overcome the disadvantages described above is desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the embodiment can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is an isometric exploded view of a miniature speaker in accordance with an exemplary embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional view of a front cover of the miniature speaker in  FIG. 1 , wherein an outer ring is ready to be coupled to a top cover. 
         FIG. 3  is a cross-sectional view of a frame of the miniature speaker in  FIG. 1 . 
         FIG. 4  is a cross-sectional view of the miniature speaker in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT 
     The present invention will hereinafter be described in detail with reference to an exemplary embodiment. 
     Referring to  FIG. 1 , a miniature speaker  100  in accordance with an exemplary embodiment of the present disclosure comprises a frame  1  providing a receiving space, a magnetic circuit  2  accommodated in the receiving space, a vibration unit  3  fixed to the frame  1 , and a front cover  4  coupled to the vibration unit  3 . The vibration unit  3  includes a membrane  30  and a voice coil  31  connected to the membrane  30  for driving the membrane  30  to vibrate, which produces audible sounds. The voice coil  13  electrically connects to an external circuit (not shown) via a plurality of contacts  5  for receiving electrical signals from the external circuit. 
     Referring to  FIG. 2 , the front cover  4  further includes an outer ring  40  and a top cover  41  coupled with the outer ring  40 . The outer ring  40  includes a sidewall and a protrusion  401  extending from an inner surface of the sidewall toward a center of the outer ring  40 . Due to the protrusion  401 , the sidewall is divided into a pressing portion  402  and a position portion  403 . The protrusion  401  comprises a first inner side  401   a  and a first top side  401   b . The position portion  403  comprises a second inner side  403   a , and a second top side  403   b . The first top side  401   b  is relatively lower than the second top side  403   b . The first inner side  401   a  is relatively closer to the center of the outer ring  40  than the second inner side  403   a . The top cover  41  includes a main body  411  and an extending portion extending from a middle portion of the main body  411  toward the outer ring  40 , thereby forming a step corresponding to the protrusion  401  of the outer ring  41 . The main body  411  includes a first outer side  411   a  corresponding to the second inner side  403   a , a first lower side  411   b  corresponding to the first top surface  401   b , and a top surface  411   c . The extending portion  412  includes a second outer side  412   a  corresponding to the first inner side  401   a.    
     Referring to  FIG. 2 , together with  FIG. 4 , while assembled, the main body  411  of the top cover  41  engages with the protrusion  401  of the outer ring  40 , with the first lower side  411   b  abutting against the first top side  401   b , the first outer side  411   a  abutting against the second inner side  403   a , and the second outer side  412   a  abutting against the first inner side  401   a . Thus, the top cover  41  is integrated with the outer ring  40  firmly. Optionally, the top surface  411   c  is coplanar with the second top side  403   b . For transmitting the sound generated by the vibration unit, the top cover  41  further includes a sound aperture  42  through the main body  411  and the extending portion  412 . 
     Referring to  FIG. 3 , the frame  1  is provided with a projecting portion  11  and a slot  10 . Referring to  FIG. 4 , together with  FIG. 3 , the magnetic circuit  2  comprises a magnetic gap for partially receiving the voice coil  31 . The magnetic circuit  2  comprises a lower plate  20 , a first magnet  21  positioned on a central portion of the lower plate  20 , a first pole plate  23  attached on a top of the first magnet  21 , a second magnet  22   a  positioned on the lower plate  20  separated from the first magnet  21 , a second pole plate  24   a  attached on a top of the second magnet  22   a , a third magnet  22   b  positioned on the lower plate  20  away from the second magnet  22   a , and a third pole plate  24   b  attached on a top of the third magnet  22   b . While assembled, the first magnet  21  locates on the lower plate  20  between the second magnet  22   a  and the third magnet  22   b . The lower plate  20  further includes a pair of recesses  200  for positioning the second and third magnets  22   a ,  22   b . When the voice coil  31  is electrified, the voice coil  31  is activated to vibrate due to the Lorenz Force generated by the magnetic circuit  2 . Accordingly, the membrane  30  is driven by the voice coil  31  to vibrate, and sounds are thus produced. Optionally, the second pole plate  24   a  and the third pole plate  24   b  are partially received in the slot  10  of the frame  1 , and the projecting portion  11  abuts against tops of the second pole plate  24   a  and the third pole plate  24   b . By virtue of this configuration, the magnetic circuit  2  is firmly positioned by the frame  1 . The pressing portion  402  of the front cover  4  presses on an edge of the membrane  30  for fixing the membrane  30  to the frame  1 . 
     By virtue of the configuration of the front cover as described above, the assembling precision of the outer ring and the top cover is ensured, and the thicknesses of the outer ring and the top cover are maintained for providing sufficient strength. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present embodiment have been set forth in the foregoing description, together with details of the structures and functions of the embodiment, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.