Patent Publication Number: US-2009220119-A1

Title: Speaker, and module, electronic apparatus, and device that use the speaker

Description:
This application is a divisional of U.S. application Ser. No. 10/591,984, filed Sep. 7, 2006, which is a U.S. national phase application of PCT International Application PCT/JP05/001735, filed Feb. 1, 2005. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a loud speaker and a module that are used in various acoustic equipment or information communication equipment, and an electronic apparatus and device such as a portable phone or a game machine. 
     BACKGROUND ART 
     A conventional device is described with reference to  FIG. 12 .  FIG. 12  is a sectional view of a conventional loud speaker. An internal magnetic circuit  4  is formed by sandwiching magnetized magnet  1  between upper plate  2  and yoke  3  in  FIG. 12 . Frame  6  is bonded to yoke  3  of magnetic circuit  4 . 
     Diaphragm  7  is bonded to a rim part of frame  6 , voice coil  8  is bonded to diaphragm  7 , and voice coil  8  is engaged in and bonded to magnetic gap  5  in magnetic circuit  4 . Protector  9  is bonded to frame  6  so as to cover diaphragm  7 . 
     As an example of a conventional device related to the present invention, reference is made to Japanese Patent Unexamined Publication No. S61-258600. 
     The loud speaker is often used in an electronic apparatus such as a portable phone. When the loud speaker is affected by electromagnetic waves, the electromagnetic waves coming from voice coil  8  of the loud speaker, are amplified by an amplifier of the electronic apparatus such as the portable phone, generates a noise component, and causes electromagnetic interference, disadvantageously. These phenomena often occur especially in a GSM (global system for mobile communications) portable phone. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the above-mentioned problems, and provides an excellent loud speaker that is hardly affected by electromagnetic waves and does not cause electromagnetic interference. 
     The loud speaker of the present invention has the following structure to address the problems. 
     The loud speaker has a frame bonded to a magnetic circuit, a diaphragm bonded to an outer periphery of the frame, and a voice coil that is bonded to the diaphragm and is partly disposed in a magnetic gap of the magnetic circuit. A protector is bonded to the frame so as to cover the diaphragm. A net made of a material containing at least metal is bonded to the protector. 
     Thanks to this structure, the net made of the material containing the metal shields electromagnetic waves to prevent the electromagnetic interference. 
     The loud speaker has a frame bonded to a magnetic circuit including a main magnet, a diaphragm bonded to an outer periphery of the frame, a voice coil that is bonded to the diaphragm and is partly disposed in a magnetic gap of the magnetic circuit, and a protector bonded to the frame so as to cover the diaphragm. A repulsion magnet is bonded to the protector at the position where the repulsion magnet faces the center pole of an upper plate or a lower plate of the magnetic circuit at a distance. 
     Thanks to this structure, a leakage flux occurring in the front surface direction of the magnetic circuit including the main magnet can be reduced by an effect of the repulsion magnet. The loud speaker is hardly affected by external electromagnetic waves, and the electromagnetic interference can be prevented in the electronic apparatus such as a portable phone using the loud speaker. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a sectional view of a loud speaker in accordance with exemplary embodiment 1 of the present invention. 
         FIG. 2  is a sectional view of a loud speaker in accordance with exemplary embodiment 2 of the present invention. 
         FIG. 3  is a sectional view of a loud speaker in accordance with exemplary embodiment 3 of the present invention. 
         FIG. 4  is a sectional view of another loud speaker in accordance with exemplary embodiment 3 of the present invention. 
         FIG. 5  is a sectional view of yet another loud speaker in accordance with exemplary embodiment 3 of the present invention. 
         FIG. 6  is a sectional view of still another loud speaker in accordance with exemplary embodiment 3 of the present invention. 
         FIG. 7  is a sectional view of a loud speaker in accordance with exemplary embodiment 4 of the present invention. 
         FIG. 8  is a sectional view of another loud speaker in accordance with exemplary embodiment 4 of the present invention. 
         FIG. 9A  is a sectional view of a loud speaker module in accordance with exemplary embodiment 5 of the present invention. 
         FIG. 9B  is a sectional view of another loud speaker module in accordance with exemplary embodiment 5 of the present invention. 
         FIG. 10A  is a sectional view of an essential part of an electronic apparatus in accordance with exemplary embodiment 6 of the present invention. 
         FIG. 10B  is a sectional view of an essential part of another electronic apparatus in accordance with exemplary embodiment 6 of the present invention. 
         FIG. 11A  is a sectional view of a device in accordance with exemplary embodiment 7 of the present invention. 
         FIG. 11B  is a sectional view of another device in accordance with exemplary embodiment 7 of the present invention. 
         FIG. 12  is a sectional view of a conventional loud speaker. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Exemplary embodiments of the present invention will be described with reference to the drawings. 
     First Exemplary Embodiment 
       FIG. 1  is a sectional view of a loud speaker in accordance with exemplary embodiment 1 of the present invention. In  FIG. 1 , internal magnetic circuit  24  is formed by sandwiching magnetized main magnet  21  between upper plate  22  and yoke  23 . 
     Resin frame  26  is bonded to yoke  23  of internal magnetic circuit  24 . The outer periphery of diaphragm  27  is bonded to a rim part of resin frame  26 , one end of voice coil  28  is bonded to diaphragm  27 , and the other end of voice coil  28  is engaged in and bonded to magnetic gap  25  of internal magnetic circuit  24 . 
     Protector  29  is bonded to resin frame  26  so as to cover diaphragm  27 , and net  30  made of a material containing at least metal is bonded to protector  29 . Protector  29  is made of a resin material. Therefore, the productivity of protector  29  can be improved, and hence the productivity of the loud speaker can be improved. 
     Net  30  is formed by knitting a thread where a foil material made of copper, nickel, or both copper and nickel is wound on a core wire made of a resin material. 
     When the core wire of net  30  includes the resin material, stretchability of net  30  is improved, and net  30  can be bonded to protector  29  without clearance. When the foil material of net  30  is made of copper or nickel, the flexibility of net  30  is improved, and the electromagnetic wave shielding effect can be increased. When protector  29  is coated with metal, the electromagnetic wave shielding effect is further increased. 
     The component ratio between the resin material and metal material in net  30  is preferably set at a required ratio that makes use of a feature of each material. The component ratio can be adjusted according to the application. For example, when the electromagnetic wave shielding effect is intended to be increased, the component ratio of the metal material is increased. When the stretchability of the net is intended to be increased, the component ratio of the resin material is increased. Especially, when the stretchability of the net is intended to be further increased, it is effective that many fine wires made of the resin material are twisted. Besides these methods, powder of the metal material may be mixed into the resin material. 
     Thanks to this structure, the electromagnetic wave is shielded by the net made of the material containing metal, and the electromagnetic interference can be prevented. Since the loud speaker is hardly affected by electromagnetic waves and the electromagnetic interference is prevented, the electromagnetic interference can be prevented in the electronic apparatus such as a portable phone using this loud speaker. 
     Second Exemplary Embodiment 
       FIG. 2  is a sectional view of a loud speaker in accordance with exemplary embodiment 2 of the present invention. This loud speaker differs from the loud speaker of embodiment 1 in that net  30  is bonded to internal magnetic circuit  24 . A part  30 A (hereinafter referred to as “net outer periphery”) of the outer periphery of net  30  is enlarged and is bonded to yoke  23  of internal magnetic circuit  24 . 
     In this structure, net  30  is grounded to internal magnetic circuit  24 , thereby improving the electromagnetic wave shielding effect. When protector  29  bonded to net  30  is coated with metal, the electromagnetic wave shielding effect can be further increased. 
     Even when net outer periphery  30 A is further enlarged and is bonded to internal magnetic circuit  24  so as to cover internal magnetic circuit  24 , the shielding effect of electromagnetic wave can be increased. 
     Third Exemplary Embodiment 
       FIG. 3  through  FIG. 6  are sectional views of loud speakers in accordance with exemplary embodiment 3 of the present invention. 
     In  FIG. 3 , internal magnetic circuit  24  is formed by sandwiching magnetized main magnet  21  between upper plate  22  and yoke  23 . Resin frame  26  is bonded to yoke  23  of internal magnetic circuit  24 . The outer periphery of diaphragm  27  is bonded to a rim part of resin frame  26 , one end of voice coil  28  is bonded to diaphragm  27 , and the other end of voice coil  28  is engaged in and bonded to magnetic gap  25  of internal magnetic circuit  24 . Protector  29  is bonded to resin frame  26  so as to cover diaphragm  27 , and repulsion magnet  39  is bonded to protector  29  at the position where repulsion magnet  39  faces upper plate  22  of magnetic circuit  24  at a distance. 
     Thanks to this structure, a leakage flux occurring in the front surface direction of internal magnetic circuit  24  including main magnet  21  can be reduced by an effect of repulsion magnet  39 . The loud speaker is hardly affected by external electromagnetic waves, and the electromagnetic interference can be prevented in the electronic apparatus such as a portable phone using the loud speaker. 
     Respective repulsion magnetic forces of main magnet  21  and repulsion magnet  39  can increase the magnetic flux density in magnetic gap  25  of internal magnetic circuit  24 , and can raise the sound pressure level of the loud speaker. 
     Next, a structure where plate  38  is bonded to repulsion magnet  39  on the opposite side to diaphragm  27  is described in  FIG. 4 . Since plate  38  is bonded to repulsion magnet  39  on the opposite side to diaphragm  27  in this structure, the effect of plate  38  can significantly reduce the leakage flux that occurs from repulsion magnet  39  itself to the outside, namely in the front surface direction. 
     By disposing plate  38  made of magnetic material on the front surface of the loud speaker, electromagnetic waves from the outside are shielded, the effect of the waves is reduced, and the electromagnetic wave interference can be reduced. 
     Comparing with the case where repulsion magnet  39  is used alone, repulsion magnet  39  can be used in a stable state at an operating point, and demagnetization due to temperature change or aging can be prevented. 
     Next, a structure where repulsion magnet  39  constitutes a magnetic circuit and is bonded to protector  29  is described with reference to  FIG. 5 . In this structure, repulsion magnet  39  is sandwiched between plate  38  and yoke  32  and constitutes the magnetic circuit including repulsion magnet  39 , and plate  38  faces upper plate  22  of internal magnetic circuit  24  including main magnet  21 . 
     Thanks to this structure, in addition to the effects of the structure shown in  FIG. 4 , the leakage flux is reduced further significantly, the electromagnetic interference is reduced, and demagnetization can be prevented by stabilizing an operation point. 
     When protector  29  is made of resin material in the present embodiment, the resin material can be formed by an injection molding method of one-shot, and the productivity of protector  29  can be improved. The productivity of the loud speaker can be improved. 
     When protector  29  is made of nonmagnetic material such as resin material, the magnetic flux generated by repulsion magnet  39  and main magnet  21  is not absorbed and hence used effectively. As these materials, in addition to the resin material, metal material such as aluminum or some stainless material is often used. 
     When protector  29  is made of magnetic material, protector  29  has a function of absorbing a magnetic flux by itself, and hence can prevent the leakage flux from coming to the front surface. The magnetic material can shield electromagnetic waves and can reduce electromagnetic interference. 
     In  FIG. 6 , a part of protector  29  is extended, and protector extended part  29 A is brought into contact with internal magnetic circuit  24  including main magnet  21 . In this case, when protector  29  is grounded to internal magnetic circuit  24 , a closed loop by the magnetic material including the front surface of the loud speaker can be formed, the leakage flux can be further reduced, and the electromagnetic interference can be reduced. 
     Fourth Exemplary Embodiment 
       FIG. 7  is a sectional view of a loud speaker in accordance with exemplary embodiment 4 of the present invention. This loud speaker differs from the loud speaker of embodiment 3 in that external magnetic circuit  24 A is used as the magnetic circuit. 
     In this structure, magnet  21 A is sandwiched between upper plate  22 A and lower plate  23 A to form external magnetic circuit  24 A. Repulsion magnet  39 A is bonded to protector  29 B at the position where repulsion magnet  39 A faces the center pole of lower plate  23 A at a distance. Other than the structure of external magnetic circuit  24 A, the structure is the same as that of embodiment 1, and further description thereof is omitted. 
     In this structure having the external magnetic circuit, the leakage flux of the external magnetic circuit is reduced by employing shielded type magnetic circuit  24 B that additionally has cancel magnet  33  and shield cover  34  as shown in  FIG. 8 . In this case in which the structure has the external magnetic circuit, shielded type magnetic circuit  24 B that additionally has cancel magnet  33  and shield cover  34  can reduce the leakage flux from the back surface of the magnetic circuit to the back surface of the loud speaker. 
     When the front surface of the loud speaker is provided with repulsion magnet  39 A that is bonded to protector  29 B at the position where repulsion magnet  39 A faces the center pole of lower plate  23 A at a distance, the leakage flux to the front surface of the loud speaker can be reduced. Therefore, the leakage flux to both the front and back surfaces of the loud speaker can be effectively reduced, and an excellent shielded loud speaker can be realized. The sound pressure level of the loud speaker can be also improved. 
     The loud speaker having a circular shape that is generally often used has been described; however, the present invention is not limited to this shape. The outer shape of the frame and the shape of the magnetic circuit may be a noncircular shape. As commonly-used shapes other than the circular shape, square, rectangle, ellipse, or a truck shape may be used. These slim shapes have especially received attention because miniaturization or compaction of the loud speaker is required. 
     Fifth Exemplary Embodiment 
       FIG. 9A  is a sectional view of a loud speaker module in accordance with exemplary embodiment 5 of the present invention. In  FIG. 9A , loud speaker  31  of embodiment 1 or 2 and electronic circuit  40  are integrated into loud speaker module  50 . 
     In loud speaker module  50 , electronic component  42  is fixed and wired to circuit board  41  to form electronic circuit  40 . Electronic circuit  40  and loud speaker  31  of embodiment 1 or 2 are integrated into loud speaker module  50 . 
     Electronic circuit  40  includes an amplifying circuit of a voice signal supplied to at least loud speaker  31 . In other words, the circuit for amplifying the processed voice signal to a level required for an output from loud speaker  31  is previously integrated with loud speaker  31  and wired internally. Therefore, only by bonding loud speaker module  50 , voice output can be easily obtained. 
     When electronic circuit  40  is applied to communication equipment such as a portable phone, electronic circuit  40  may include, in addition to the amplifying circuit, a circuit required for communication such as a wave detecting circuit, a modulating circuit, or a demodulating circuit, a driving circuit used for a display means such as liquid crystal, and various circuits such as a power supply circuit or a charging circuit. 
     Loud speaker  31  and electronic circuit  40  are conventionally produced separately, undergo respective inspection processes and physical distribution processes, and are supplied to a production site of an electronic apparatus such as a portable phone. However, thanks to this structure, loud speaker  31  and electronic circuit  40  are integrated and modularized, and hence the production processes, inspection processes, and physical distribution processes can be unified, thereby significantly reducing the cost. Therefore, inexpensive loud speaker module  50  where loud speaker  31  is bonded to electronic circuit  40  can be provided. 
     Similarly,  FIG. 9B  is a sectional view of another loud speaker module in accordance with exemplary embodiment 5 of the present invention. In  FIG. 9B , loud speaker  35  of embodiment 3 or embodiment 4 and electronic circuit  40  are integrated into a loud speaker module. Advantages of such a structure are the same as for the structure of  FIG. 9A . 
     Sixth Exemplary Embodiment 
       FIG. 10A  is a sectional view of an essential part of a portable phone as an electronic apparatus in accordance with exemplary embodiment 6 of the present invention. In  FIG. 10A , portable phone  80  includes loud speaker  31  of embodiment 1 or 2. 
     Loud speaker  31 , electronic circuit  40 , various components such as display module  60  such as liquid crystal, a module, and the like are mounted in exterior case  70  to form the essential part of portable phone  80 . 
     Thanks to this structure, loud speaker  31  is hardly affected by electromagnetic waves and electromagnetic interference does not occur, so that electromagnetic interference can be prevented in an electronic apparatus such as portable phone  80  employing loud speaker  31 . 
       FIG. 10B  is a sectional view of an essential part of another portable phone as an electronic apparatus in accordance with exemplary embodiment 6 of the present invention. In  FIG. 10B , portable phone  80  includes loud speaker  35  of embodiment 3 or 4. 
     Loud speaker  35 , electronic circuit  40 , various components such as display module  60  such as liquid crystal, a module, and the like are mounted in exterior case  70  to form the essential part of portable phone  80 . 
     Thanks to this structure, leakage flux of an electronic apparatus such as portable phone  80  can be reduced, the electronic apparatus such as portable phone  80  is hardly affected by external electromagnetic waves, and electromagnetic interference can be prevented. By improving the sound pressure level of loud speaker  35 , the sound pressure level of the electronic apparatus such as portable phone  80  can be improved. Therefore, the electronic apparatus such as portable phone  80  can save energy. 
     Seventh Exemplary Embodiment 
       FIG. 11A  is a sectional view of an automobile as a device in accordance with exemplary embodiment 7 of the present invention. As shown in  FIG. 11A , in automobile  90 , loud speaker  31  of embodiment 1 or 2 is assembled into a rear tray or a front panel, and is used as a part of a car navigation system or car audio system. 
     Thanks to this structure, loud speaker  31  is hardly affected by electromagnetic waves and electromagnetic interference does not occur. Therefore, electromagnetic interference can be prevented in a device such as automobile  90  employing loud speaker  31 . 
       FIG. 11B  is a sectional view of another automobile as a device in accordance with exemplary embodiment 7 of the present invention. As shown in  FIG. 11B , in automobile  90 , loud speaker  35  of embodiment 3 or 4 is assembled into the rear tray or the front panel, and is used as a part of the car navigation system or car audio system. 
     Thanks to this structure, leakage flux from loud speaker  35  of the device such as automobile  90  can be reduced, the device such as automobile  90  is hardly affected by external electromagnetic waves, and electromagnetic interference can be prevented. By improving the sound pressure level of loud speaker  35 , the sound pressure level of the device such as automobile  90  can be improved. Therefore, the fuel consumption of the device such as automobile  90  can be reduced, and global environment can be protected. 
     INDUSTRIAL APPLICABILITY 
     A loud speaker, a loud speaker module, and an electronic apparatus and device of the present invention can be applied to video acoustic equipment or information communication equipment that require measures against electromagnetic interference, an electronic apparatus such as a game machine, and a device such as an automobile.