Patent Publication Number: US-8538060-B2

Title: Voice coil lead wire and loudspeaker using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 200910109566.7, filed on Aug. 5, 2009, in the China Intellectual Property Office, the contents of which are hereby incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to coil lead wires and loudspeakers using the same. 
     2. Description of Related Art 
     A voice coil lead wire is one component of a loudspeaker. A voice coil and an external audio input device can be electrically connected by the coil lead wire. 
     Presently, the voice coil lead wire is formed by intertwisting a plurality of metal wires. However, the metal wires have poor strength. A bent voice coil lead wire can cause a fatigue fracture of the metal wires in the voice coil lead wire and make the loudspeaker inoperative. Thus, the lifespan of the loudspeaker is reduced. 
     What is needed, therefore, is to provide a voice coil lead wire resisting fatigue fracture, and a loudspeaker using the same. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the embodiments 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 embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a structural schematic view of a first embodiment of a voice coil lead wire. 
         FIG. 2  is a sectional view of the voice coil lead wire of  FIG. 1 , taken along line II-II. 
         FIGS. 3 and 4  are a structural schematic view of a carbon nanotube wire structure in the voice coil lead wire of  FIG. 1 . 
         FIG. 5  is a Scanning Electron Microscope (SEM) image of a non-twisted carbon nanotube wire in the voice coil lead wire of  FIG. 1 . 
         FIG. 6  is an SEM image of a twisted carbon nanotube wire in the voice coil lead wire of  FIG. 1 . 
         FIG. 7  is a structural schematic view of a second embodiment of a voice coil lead wire. 
         FIG. 8  is a structural schematic view of a loudspeaker using the voice coil lead wire. 
         FIG. 9  is a sectional view of the loudspeaker of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
     Referring to  FIGS. 1 and 2 , one embodiment of a voice coil lead wire  100  includes a core wire structure  102  and a lead wire structure  104 . The lead wire structure  104  is wound around the axis of the core wire structure  102  in a helix manner. 
     The voice coil lead wire  100  can be fabricated by fixing the core wire structure  102  and winding the lead wire structure  104  on the surface of the core wire structure  102  in a helix manner around the axis of the core wire structure  102 . 
     The lead wire structure  104  can be wound around the axis of the core wire structure  102  in a clockwise or anticlockwise direction. The axis direction of the lead wire structure  104  extends from one end of the core wire structure  102  to the other end thereof in a helix manner. 
     A plurality of helix portions, formed by winding the lead wire structure  104  into a plurality of windings around the core wire structure  102 , are connected to each other. The helix angle of each helix portion are not limited. The number of the windings is related to the degree of the helix angle of every helix portion. The smaller the helix angle, the greater the number of the windings around the core wire structure  102 , and the greater the weight of the lead wire structure  104 . The helix angles of the plurality of helix portions can be the same or different. In one embodiment, the helix angles of the plurality of helix portions are the same and ranges from about 2 degrees to about 30 degrees. A diameter of the voice coil lead wire  100  can be substantially equal to a diameter of the core wire structure  102  plus twice of the diameter of the lead wire structure  104 . In use, the voice coil lead wire  100  is connected to a voice coil of a speaker. The voice coil oscillates linearly such that the voice coil lead wire  100  is repeatedly deformed in response to the oscillation of the coil. The voice coil lead wire  100  applies a load to the voice coil. Thus, the weight of the voice coil lead wire  100  will influence the oscillation of the voice coil. The greater the weight of the voice coil lead wire  100 , the greater the load of the voice coil. Therefore, if the voice coil lead wire  100  is too heavy, the voice coil cannot oscillate properly, thereby causing a distorted sound from the loudspeaker. Thus, the mechanical strength of the voice coil lead wire  100  should be high enough such that the voice coil lead wire  100  does not break easily and the diameter of the voice coil lead wire  100  is as small as possible. In one embodiment, the diameter of the voice coil lead wire  100  is in a range from about 0.1 millimeters (mm) to about 50 mm. 
     The core wire structure  102  includes at least one carbon nanotube wire structure. The carbon nanotube wire structure includes a plurality of carbon nanotubes. The carbon nanotubes can be single-walled, double-walled, or multi-walled carbon nanotubes. A diameter of each single-walled carbon nanotube can range from about 0.5 nanometer (nm) to about 10 nm. A diameter of each double-walled carbon nanotube can range from about 1 nm to about 15 nm. A diameter of each multi-walled carbon nanotube can range from about 1.5 nm to about 50 nm. The diameter of the carbon nanotube wire structure can be set as desired. Referring to  FIGS. 3 and 4 , the carbon nanotube wire structure  1020  includes at least one carbon nanotube wire  1022 . The carbon nanotube wire structure  1020  can be a bundle structure composed of a plurality of carbon nanotube wires  1022  substantially parallel to each other, or the carbon nanotube wire structure  1020  can be a twisted structure composed of a plurality of carbon nanotube wires  1022  twisted together. 
     The carbon nanotube wire  1022  can be a non-twisted carbon nanotube wire or a twisted carbon nanotube wire. Referring to  FIG. 5 , the non-twisted carbon nanotube wire includes a plurality of carbon nanotubes substantially oriented along a same direction (e.g., a direction along the length of the non-twisted carbon nanotube wire). The carbon nanotubes are substantially parallel to the axis of the non-twisted carbon nanotube wire. Specifically, the non-twisted carbon nanotube wire includes a plurality of carbon nanotubes joined end-to-end by van der Waals attractive force therebetween. A length of the non-twisted carbon nanotube wire can be arbitrarily set as desired. A diameter of the non-twisted carbon nanotube wire can range from about 0.5 nm to about 100 microns (μm). The non-twisted carbon nanotube wire can be formed by treating a drawn carbon nanotube film with an organic solvent. Specifically, the drawn carbon nanotube film is treated by applying the organic solvent to the drawn carbon nanotube film to soak the entire surface of the drawn carbon nanotube film. After being soaked by the organic solvent, the adjacent parallel carbon nanotubes in the drawn carbon nanotube film will bundle together, due to the surface tension of the volatile organic solvent as the organic solvent volatilizes, and thus, the drawn carbon nanotube film will be shrunk into a non-twisted carbon nanotube wire. The organic solvent can be ethanol, methanol, acetone, dichloroethane or chloroform. In one embodiment, the organic solvent is ethanol. The non-twisted carbon nanotube wire treated by the organic solvent has a smaller specific surface area and a lower viscosity than that of the drawn carbon nanotube film untreated by the organic solvent. An example of the non-twisted carbon nanotube wire is taught by US Patent Application Publication US 2007/0166223 to Jiang et al. 
     The twisted carbon nanotube wire can be formed by twisting a drawn carbon nanotube film by using a mechanical force to turn the two ends of the drawn carbon nanotube film in opposite directions. Referring to  FIG. 6 , the twisted carbon nanotube wire includes a plurality of carbon nanotubes oriented around an axial direction of the twisted carbon nanotube wire. The carbon nanotubes are aligned in a helix around the axis of the twisted carbon nanotube wire. More specifically, the twisted carbon nanotube wire includes a plurality of successive carbon nanotube segments joined end-to-end by van der Waals attractive force therebetween. Each carbon nanotube segment includes a plurality of carbon nanotubes substantially parallel to each other and combined by van der Waals attractive force. The carbon nanotube segment has arbitrary length, thickness, uniformity and shape. A length of the twisted carbon nanotube wire can be arbitrarily set as desired. A diameter of the twisted carbon nanotube wire can range from about 0.5 nm to about 100 μm. Further, the twisted carbon nanotube wire can be treated with a volatile organic solvent before or after being twisted. After being soaked by the organic solvent, the adjacent parallel carbon nanotubes in the twisted carbon nanotube wire will bundle together, due to the surface tension of the organic solvent as the organic solvent volatilizes. The specific surface area of the twisted carbon nanotube wire will decrease, and the density and strength of the twisted carbon nanotube wire will be increased. 
     A diameter of the carbon nanotube wire structure  1020  can be set as desired. In one embodiment, the diameter of the carbon nanotube wire structure  1020  ranges from about 50 μm to about 20 mm. 
     In addition, the core wire structure  102  can be a bundle structure composed of a plurality of carbon nanotube wire structures  1020  substantially parallel to each other. The core wire structure  102  can also be a twisted structure composed of a plurality of carbon nanotube wire structures  1020  twisted together. 
     Referring to  FIG. 2 , the lead wire structure  104  includes at least one lead wire  1042 . The lead wire structure  104  can be a bundle structure composed of a plurality of lead wires  1042  substantially parallel to each other. The lead wire structure  104  can also be a twisted structure composed of a plurality of lead wires  1042  twisted together. The lead wire structure  104  can be made of a material having a small density and a high conductivity, such as copper (Cu), aluminum (Al), or any combination alloy thereof. In one embodiment, the lead wire structure  104  is a twisted copper structure wound on the surface of the core wire structure  102  in a helix manner. 
     Furthermore, an insulative layer  1044  can be wrapped around the surface of each lead wire  1042  or the surface of the lead wire structure  104 . The insulative layer  1044  can be formed by coating an insulative lacquer on the surface of each lead wire  1042  or the surface of the lead wire structure  104 . The insulative layer  1044  can be made of plastic or rubber. In one embodiment, the insulative layer  1044  is wrapped around the surface of the lead wire structure  104 . The insulative layer  1044  can prevent the lead wire  1042  from corrosion due to exposure to moisture in the air, thereby prolonging the life of the voice coil lead wire  100 . 
     The carbon nanotube wire structure  1020  can improve the strength and bend resistance of the voice coil lead wire  100 , because the carbon nanotube wire structure  1020  is composed of a plurality of carbon nanotubes joined end-to-end by van der Waals attractive force therebetween, and therefore, has a high strength and bend resistance. In addition, the conductivity of the voice coil lead wire  100  is improved because the carbon nanotubes extend along the axis direction of the carbon nanotube wire structure  1020 , and the carbon nanotubes have a good conductive property along the length of the carbon nanotubes. Furthermore, even when a fatigue fracture of the lead wires  1042  in the voice coil lead wire  100  has occurred, the carbon nanotube wire structure  1020  can still electrically conduct the audio electrical signals, thereby prolonging the lifetime of the loudspeaker. 
     Referring to  FIG. 7 , a second embodiment of the voice coil lead wire  200  includes a core wire structure  202  and a lead wire structure  204  twisted with each other. 
     The voice coil lead wire  200  can be a twisted structure. The twisted voice coil lead wire  200  can be formed by disposing the core wire structure  202  and the lead wire structure  204  in a substantially parallel manner, and twisting the core wire structure  202  and the lead wire structure  204  by using a mechanical force to turn the opposite ends of the core wire structure  202  and the lead wire structure  204  in opposite directions. Thus, the core wire structure  202  and the lead wire structure  204  are twisted with each other. 
     The core wire structure  202  and the lead wire structure  204  extend from one end of the voice coil lead wire  100  to the other end of the voice coil lead wire  100 , in a helix manner around the axis of the voice coil lead wire  200 . Helix directions of the core wire structure  202  and the lead wire structure  204  are the same. 
     The helix angle of a plurality of helix portions, formed by twisting the lead wire structure  204  and core wire structure  202  into a plurality of laps, are not limited, and can be set as desired. The number of the windings is related to the helix angle of each helix portion. The smaller the helix angle, the greater the number of the windings of the core wire structure  202  and the lead wire structure  204 , the greater the volume ratio of the lead wire structure  204  and core wire structure  202  per unit volume of the voice coil lead wire  200 , and the greater the weight of the voice coil lead wire  200 . In one embodiment, the helix angles range from about 2 degrees to about 30 degrees. 
     Referring to  FIGS. 8 and 9 , one embodiment of a loudspeaker  10  using the first or second embodiments of the voice coil lead wire  100 ,  200  includes a magnetic system  12 , a vibrating system  14 , and a supporting system  16 . 
     The magnetic system  12  includes a back plate  121  having a center pole  123 , a top plate  125 , and a magnet  122 . The back plate  121  and the top plate  125  are coaxial, and opposite to each other. The magnet  122  is fixed between the top plate  125  and the back plate  121 . The top plate  125  and the magnet  122  are annular in shape. The top plate  125  and the magnet  122  cooperatively define a column space. The center pole  123  projects into the column space. The center pole  123 , the magnet  122 , and the top plate  125  are dimensioned and shaped to cooperatively define an annular magnetic gap  124 . 
     The vibrating system  14  includes a diaphragm  142 , a voice coil bobbin  144 , a voice coil  146 , a damper  143  defining a through hole  1430 , and a voice coil lead wire  100 . The diaphragm  142  has a funnel configuration and includes a dome  1420  protruding from a center of the bottom thereof. The bobbin  144  surrounds the center pole  123 , and is disposed in the magnetic gap  124  to move along an axial direction of the center pole  123 . 
     The bobbin  144  extends through the through hole  1430  to fix the diaphragm  142  and the damper  143  thereon. The voice coil  146  is received in the magnetic gap  124 , and wound around the bobbin  144 . The voice coil lead wire  100  includes a first end (not labeled) electrically connected to the voice coil  146  and a second end (not labeled) attached to the supporting system  16 . 
     The supporting system  16  includes a frame  162  which is used to contain the vibrating system  14 . The frame  162  can be frustum and may have a cavity  161  and a bottom  163  with an opening  111 . The bobbin  144  extends through the opening  111 , the top plate  125 , and the magnet  122 , and is received in the magnetic gap  124  such that the magnetic system  12 , the vibrating system  14 , and the supporting system  16  can be assembled together. The cavity  161  can receive the diaphragm  142  and the damper  143 . The bottom  163  of the frame  162  is fixed to the top plate  125  of the magnetic system  12 . The diaphragm  142  and the damper  143  are fixed to the frame  162 . Additionally, a terminal  164  is disposed on the frame  162 . The second end of the voice coil lead wire  100  can be directly connected to the terminal  164 . 
     Furthermore, the voice coil lead wire  100  can be fixed to a surface of the diaphragm  142 , and extend to the terminal  164 . The voice coil lead wire  100  can be adhered to the surface of the diaphragm  142  by an adhesive, or fixed to the surface of the diaphragm  142  by a groove defined in the diaphragm  142 . The second end of the voice coil lead wire  100  can be electrically connected to the terminal  164  by arbitrary means. For example, a short metal wire can be welded to a conductive portion of the terminal  164 , and then adhered to the voice coil lead wire  100  by an adhesive. The voice coil lead wire  100  can also be directly and electrically connected to the terminal  164 . 
     The voice coil lead wire  100 ,  200  include a carbon nanotube wire structure. The carbon nanotube wire structure can improve the strength and bend resistance of the voice coil lead wire  100 ,  200 , because the carbon nanotube wire structure is composed of a plurality of carbon nanotubes joined end-to-end by van der Waals attractive force therebetween, which have a high strength and bend resistance. In addition, the conductivity of the voice coil lead wire  100 ,  200  is improved because the carbon nanotubes extend along the axis direction of the carbon nanotube wire structure, and the carbon nanotubes have a good conductive property along the length of the carbon nanotubes. Thus, the lifetime of the loudspeaker  10  can be prolonged. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, 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 disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.