Patent Publication Number: US-2005123166-A1

Title: Structure of speaker

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to a sound generating device and, more particularly, to an improved structure of speaker.  
      2. Description of Related Art  
      In the development of various audio and video multimedia devices, the quality of audio signal is improving as well as that of video signals day by day. Notwithstanding the current technology can integrate magnificent sound signals, superior sound quality still needs a good speaker to perform. Since the sound of a multimedia audio and video equipment is produced by transforming an electric signal into a sound wave via a speaker, the speaker need to be improved to obtain sound signals in high quality.  
      As shown in  FIG. 1 , a conventional speaker  1  has an upper cover  11 , a base  12 , a permanent magnet  13 , a coil  14  and a membrane  15 . The permanent magnet  13  is mounted in a notch  121  of the base  12  with the poles distributed as shown in the diagram (N-pole on the top and S-pole at the bottom). The coil  14  is wound around the prefabricated groove  131  with the top surface thereof adhered to the membrane  15  by an adhesive. Furthermore, two external wires  141  extracted from the coil  14  are electrically connected to an external power supply (not shown).  
      In operation, when the terminals A and B of the two external wires  141  are connected respectively to the positive and negative electrode of the external power supply, the coil  14  has a polarity distribution in which the top half is N-pole and the bottom half is S-pole due to the electromagnetic induction. The magnetic force between the coil  14  and the permanent magnet  13  then forces the coil  14  to move upward and simultaneously makes the membrane  15  to move upward. Similarly, when the two terminals A and B of the external wires  141  are connected respectively to the negative and positive electrode of the external power supply, the coil  14  will have a polarity distribution in which the top half is S-pole and the bottom half is N-pole due to the electromagnetic induction. The magnetic force between the coil  14  and the permanent magnet  13  then forces the coil  14  to move downward and simultaneously makes the membrane  15  to move downward. Thus, by changing the current direction flowing through the coil  14 , we can make the membrane  15  vibrate with various amplitudes in response to the electrical signals applied to the coil  14 , and push the air to generate sound.  
      For this conventional speaker  1 , since the coil  14  is mostly made up of self-adhesive wires having weak tensile strength, and vibrates together with the membrane  15 , the coil  14  is quite easy to break during the vibration process and the life of the speaker is shortened.  
      As shown in  FIG. 2 , another conventional speaker  2  has an upper cover  20 , a bottom cover  21 , a ring type housing  22 , a disk type magnet  23  with a magnetic pillar  231  extending upwardly from center, a ring type permanent magnet  24  with S-pole on the upper part and N-pole at the lower part, a membrane  25 , a magnetic sheet  26 , and a coil  27 . The ring type permanent magnet  24  is mounted on the inner sidewall of the ring type housing  22 , and the disk type magnet  23  is attached to the outer bottom face of the ring type housing  22 . Besides, the coil  27  is wound along the cylindrical surface of the magnetic pillar  231 , and the membrane  25  is mounted on the top face of the ring type housing  22  with a magnetic sheet  26  attached to the center section of the membrane  25 . Moreover, two external wires  271  are extracted from the coil  27  to be connected to an external power supply (not shown).  
      In operation, when terminals A and B of the two external wires  271  are connected to the negative and positive electrodes, respectively, the coil  27  electro-magnetically inducts the magnetic pillar  231  to have a polarity distribution in which the top half is N-pole and the bottom half is S-pole. The magnetic force between the magnetic pillar  231  and the magnetic sheet  26  then pushes the membrane  25  to move downward. Similarly, when the two terminals A and B of the external wires  271  are connected respectively to the positive and negative electrode of the external power supply, the coil  27  electro-magnetically inducts the magnetic pillar  231  to have a polarity distribution in which the upper part is S-pole and the lower part is N-pole. The magnetic force between the magnetic pillar  231  and the magnet sheet  26  then pushes the membrane  25  to move upward. Thus, by changing the current direction flowing through the coil  27 , we can make the membrane  25  to vibrate with various amplitudes in response to the electrical signals applied to the coil  27 , and push the air to generate sound.  
      For this conventional speaker  2 , however, since the magnetic sheet  26  mounted on top of the membrane  25  has only one polarity, the magnetic force between the magnetic sheet  26  and the magnetic pillar  231  is weak and makes the membrane  25  to vibrate with limited amplitudes. Therefore, the voice of the generated sound is limited.  
      In order to effectively improve the sound quality of audio and video multimedia equipment and to solve the above-mentioned problems, this invention discloses an improved speaker structure. The improved speaker structure is easy to manufacture and is low in the cost. It also effectively increases the efficiency of transforming electric signals to sound waves. The speaker structure can be used as sound generating devices in various multimedia equipments such as a mobile phone, notebook, and hi-fi equipment.  
     BRIEF SUMMARY OF THE INVENTION  
      In view of the above-mentioned problems, one object of the invention is to provide a speaker structure that can effectively transform an electronic signal into a sound wave, and has longer life and increased sound output.  
      The speaker structure according to this invention includes at least a bobbin, a coil, a membrane, and a magnetic assembly. The coil is wound around the side surface of the bobbin, and the membrane is disposed at one end of the bobbin. The magnetic assembly is suspended in the through hole of the bobbin with one end thereof connected to the membrane.  
      In one of the embodiment, the polarity of an end of the magnetic assembly connected to the membrane is opposite to the polarity of the middle section of the magnetic assembly. Furthermore, the radial centerline of the magnetic assembly is in alignment with the radial centerline of the coil. In addition, the length above (or beneath) the centerline of the coil is greater than the half-length above (or beneath) the centerline of the magnetic assembly and less than the length above (or beneath) the centerline of the magnetic assembly.  
      One of the advantages of the speaker structure of the invention is the ease of manufacturing and assembly. Besides, the coil has sufficient winding space, and does not break during operation process. Furthermore, the magnetic force derived can generate loud sound and the vibration level of the magnetic assembly is uniform. Also, the speaker structure is adaptable to large-scale and micro-scale speaker. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a sectional diagram illustrating a conventional speaker structure.  
       FIG. 2  is a sectional diagram illustrating another conventional speaker structure.  
       FIG. 3A  is a sectional diagram illustrating speaker structure according to one embodiment of the invention.  
       FIG. 3B  is a schematic diagram illustrating the magnetic force action between the magnetic assembly and the coil of the speaker structure shown in  FIG. 3A  in a first condition.  
       FIG. 3C  is a schematic diagram illustrating the magnetic force effect between the magnetic assembly and the coil of the speaker structure shown in  FIG. 3A  in a second condition.  
       FIG. 4  is a sectional diagram illustrating speaker structure according to another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As shown in  FIG. 3A , a speaker structure  3  of the first embodiment of the invention includes an upper housing  31   a  and lower housing  31   b,  a bobbin  32 , a coil  33 , a magnetic assembly  34  and two membranes  35   a  and  35   b.  The upper housing  31   a,  lower housing  31   b,  and the bobbin  32  are made of plastics. The magnetic assembly  34  can be made from materials such as permanent magnet or other materials with magnetism such as plastic magnet.  
      The bobbin  32  has a through hole  321  and two partition surfaces  322  and  323  extending outwardly in radial from the outer side surface  324 . Furthermore, the partition surfaces  322  and  323  extend upwards and downwards to form flanges  3221  and  3231 , respectively. The coil  33  is wound on the outside surface  324  of the bobbin  32  and between the two partition surfaces  322  and  323 . Furthermore, two external wires  332  are extracted from the coil  33  to be connected to an external power supply. Two membrane  35   a  and  35   b  are disposed at upper and lower ends of the bobbin  32  and fixed to the flanges  3221  and  3231 , respectively, and there exists a gap between the partition surface  322  ( 323 ) and its corresponding membrane  35   a  ( 35   b ). Besides, the magnetic assembly  34  is suspended in the through hole  321  and both ends thereof are connected to the two membranes  35   a  and  35   b,  respectively.  
      On the other hand, the polarities of both ends of the magnetic assembly  34  connecting to the membranes  35   a  and  35   b  are the same but opposite to the polarity of the middle section. In this embodiment, the magnetic assembly  34  is formed by stacking two permanent magnets with the N-pole connected to N-pole and S-pole connected to S-pole. As a result, the polarity of the top and bottom ends of the magnetic assembly  34  are both N-pole, and the middle section is S-pole. In addition, to ensure the magnetic force arisen between the magnetic assembly  34  and the coil  33  can bring out the expected effect, the radial centerline  341  of the magnetic assembly  34  is in alignment with the radial centerline  331  of the coil  33 . Besides, the length H above (or beneath) the centerline  331  of the coil  33  must be greater than half of the length L above (or beneath) the centerline  341  of the magnetic assembly  34  and less than the length L above (or beneath) the centerline  341  of the magnetic assembly  34 . That is, L/2&lt;H&lt;L.  
      In this embodiment, each of the permanent magnets forming the magnetic assembly  34  has a through hole in the center (not shown). Which is to connect all permanent magnets forming the magnetic assembly  34  with the two membranes  35   a  and  35   b  using rivets  36 . This method can form a secure connection between the magnetic assembly  34  and the two membranes  35   a  and  35   b  to prevent them from breaking away during vibrating process. In addition to this method, the magnetic assembly  34  can also be adhered to the membranes  35   a  and  35   b  using an adhesive.  
      As shown in  FIG. 3B , when the terminals A and B of the two external wires  332  of the coil  33  are connected respectively to a positive and a negative electrodes of an external power supply, the coil  33  generates a magnetic field with the upper half being N-pole, and the lower half being S-pole. The radial centerline  341  of the magnetic assembly  34  is in alignment with the radial centerline  331  of the coil  33 . The length H above the centerline  331  of the coil  33  is greater than half of the length L above the centerline  341  of the magnetic assembly  34 . Therefore, the magnetic force arisen between the magnetic field of the coil  33  and the magnetic assembly  34  pushes the magnetic assembly  34  to move upward and simultaneously makes the membrane  35   a  to move upward. Likewise, referring to  FIG. 3C , when the terminals A and B of the two external wires  332  of the coil  33  are connected respectively to a negative and a positive electrodes of an external power supply, the coil  33  generates a magnetic field with the upper half being S-pole, and lower half being N-pole. The magnetic force arisen between the magnetic field and the magnetic assembly  34  pushes the magnetic assembly  34  to move downward and simultaneously makes the membrane  35   a  to move downward.  
      By changing the polarity of the electrodes connecting to the two terminals A and B of the two external wires  332  of the coil  33 , the magnetic assembly  34  is made to vibrate in the through hole  321  of the bobbin  32  and push the membrane  35   a  and  35   b  to vibrate and push the air to generate sound.  
      As shown in  FIG. 4 , the speaker  3 ′ according to second embodiment of the invention has a different bobbin  32 ′ from the one in the first embodiment of the invention. However, the rests are the same and will not be described again hereafter.  
      In this embodiment, the bobbin  32 ′ has a through hole  321  to accommodate the magnetic assembly  34 . It also has partition surfaces  325 ,  326 ,  327 ,  328  and  329  extending outwardly in radial from the outer side surface  324 ′. Furthermore, the partition surfaces  325  and  329  extend upwards and downward to form flanges  3251  and  3291  respectively. The coil  33  is wound around the outside surface  324 ′ of the bobbin  32 ′ in sections between partition surfaces  325  and  326 , between partition surfaces  326  and  327 , between partition surfaces  327  and  328 ,and between partition surfaces  328  and  329 . Furthermore, there are two external wires  332  extracted from the coil  33  to be connected to an external power supply. The two membranes  35   a  and  35   b  are disposed at the two ends of the bobbin  32  and are fixed to the flanges  3251  and  3291 . Therefore, there exists a gap between the partition surface  325  ( 329 ) and its corresponding membrane  35   a  ( 35   b ). In addition, the magnetic assembly  34  is suspended in a through hole  321 ′ with its upper and lower ends connected to two membranes  35   a  and  35   b  respectively.  
      Besides, the radial centerline  341  of the magnetic assembly  34  is in alignment with the radial centerline  331 ′ of the coil  33 . In addition, the length H′ above (or beneath) the centerline  331 ′ of the coil  33  is greater than half of the length L above (or beneath) the centerline  341  of the magnetic assembly  34 , and is less than the length L above (or beneath) the centerline  341  of the magnetic assembly  34 .  
      In comparison with the conventional speaker shown in  FIG. 2 , the area for magnetic action lines between the magnetic assembly  34  and the coil  33  to pass through is bigger for the speaker structure in each of the embodiments of the invention. This provides sufficient magnetic force to increase the amplitude of vibration of the membrane  35   a  and  35   b  to generate loud sound. Furthermore, in comparison with the conventional speaker shown in  FIG. 1 , the coil  33  used in the speaker structure of the invention is motionless and thus prevents itself from breaking during the vibration process.  
      To sum up, the invention has been disclosed with illustrative embodiments described hereinbefore. These embodiments are used to exemplify but not to limit the invention. Therefore, any changes and modifications of the speaker structure without departing from the substantial spirit and scope are considered to lie within the scope of the invention as defined by the appended claims.