Patent Grant
7864976
The present invention claims priority under 35 U.S.C. §119 to Japanese Application No. 2005-167530 filed Jun. 7, 2005, the contents of which are incorporated herein by reference.
An embodiment of the present invention may relate to a speaker. More specifically, an embodiment of the present invention may relate to a speaker which detects an operating state of the diaphragm of the speaker.
In some audio speakers, a Motion Feed Back (“MFB”) circuit is mounted as a technique to improve the sound quality of the speaker. The MFB circuit detects the operating state of a vibrating diaphragm through an electric signal showing audio information (hereinafter referred to as an “audio signal”) that is inputted to a speaker, and feedback-controls the diaphragm based on the detected result. The distortion of sound, which is especially likely to be occurred in a low tone range, can be canceled. Therefore, it is sometimes mistakenly assumed that the MFB circuit is effective to be utilized in a small-sized speaker in which reproduction in a low tone range is difficult.
For example, the following five references with regard to an MFB circuit are known; Japanese Patent Laid-Open No. Sho 52-79644, Japanese Patent Laid-Open No. Sho 53-12319, Japanese Patent Laid-Open No. Sho 53-12320, Japanese Patent Laid-Open No. Sho 53-12321, and Japanese Utility Model Laid-Open No. Sho 57-96589. In these references, the operating state of the diaphragm is detected by detecting the variation of an electrostatic capacity formed between electrodes. More specifically, an electrode (hereinafter, referred to as “movable electrode”) is fixed to a diaphragm or to an electromagnetic coil which is referred to as a voice coil bobbin and that causes the diaphragm to vibrate, and another electrode (hereinafter, referred to as “fixed electrode”) is fixed so as to face the movable electrode. An electrostatic capacity, which is varied by the movable electrode being moved relative to the fixed electrode, is detected and outputted as a detection signal. After that, the detection signal corresponding to the electrostatic capacity and an audio signal are compared with each other by a comparison device (for example, a CPU), and then the operation of the diaphragm is appropriately controlled on the basis of the compared result, i.e., the difference between the output level of the detection signal and the output level of the audio signal.
However, the electrostatic capacity that is formed between the electrodes is very small, for example, from several picofarad (pF) to several hundred of pF. Therefore, the electrostatic capacity is affected and varied by a small amount of electromagnetic waves, static electricity, or the like. For example, a diaphragm is commonly structured to vibrate by an excitation effect between a voice coil bobbin, an iron core that is inserted into the voice coil bobbin and referred to as a center pole, and a magnet that generates a magnetic flux passing through the voice coil bobbin and the center pole. However, the electrostatic capacity between the electrodes is affected and varied by an exciting current flowing through the voice coil bobbin. Further, some of electronic components that are incorporated into a speaker emit an electromagnetic wave although it may be weak, and the electrostatic capacity may be varied by the electromagnetic wave that transmits to the electrodes. Further, the electrostatic capacity between the electrodes may be affected by friction accompanied with mechanical phenomena such as vibration of components which are incorporated in the speaker, static electricity caused by various electromagnetic phenomena in the inside and the outside of the speaker, electromagnetic waves which are outputted by electronic equipment installed around the speaker, or the like. As described above, in the above-mentioned prior art, the electrostatic capacity varies and the electrostatic capacity formed between the electrodes is unable to be accurately detected.
Further, a movable electrode used in the above-mentioned references is made of a metal foil. The metal foil is moved in a reciprocating manner in a constant magnetic field to generate an eddy current and thus a correct electrostatic capacity is not obtained. Therefore, an operating state of the diaphragm cannot be accurately detected and thus distortion of a sound in a low tone range is not sufficiently reduced.
In view of the problems described above, an embodiment of the present invention may advantageously provide a speaker in which an electrostatic capacity formed between electrodes can be accurately detected without being affected by disturbance noise such as an electromagnetic wave or static electricity.
Thus, according to an embodiment of the present invention, there may be provided a speaker comprising a voice coil bobbin which is provided with a nonmetallic pipe body as a base of the voice coil bobbin, a first nonmagnetic and electric conductor film which is formed on the inner peripheral face of the pipe body, and a second electric conductor film which is formed on the outer peripheral face of the pipe body such that the first electric conductor film is covered by the second electric conductor film through the pipe body, and a center pole. An electrostatic capacity that is formed between the voice coil bobbin and the center pole is detected and is outputted as an electric signal.
Therefore, in this speaker, since the second electric conductor film may block an electromagnetic wave from the outside, an electrostatic capacity which is formed between the first electric conductor film and the center pole is maintained and thus the variation of the electrostatic capacity which is formed between the voice coil bobbin and the center pole can be accurately detected. Further, reliability of a detected result is enhanced. As a result, for example, the detected result is effectively utilized in the MFB circuit and sound distortion from a speaker which is a conventional problem can be reduced. Accordingly, a low tone range similar to one found in a large speaker can be realized even in a small speaker.
In accordance with an embodiment, insulator films are formed on the first and the second electric conductor films. When an insulator film is formed on the first electric conductor film, relative permittivity can be enhanced. In other words, an electrostatic capacity formed between the first electric conductor film and the center pole increases, and thus an effect of disturbance noise can be reduced. In addition, since the electrostatic capacity increases, even when a weak electromagnetic wave reaches from the outside, its effect can be reduced and thus a stable detection result can be obtained. In addition, when an insulator film is formed on the second electric conductor film, the second electric conductor film can be electrically insulated from disturbance noise. Further, for example, a lead wire that is wound around the voice coil bobbin and the second electric conductor film can be electrically insulated by the insulator film. Therefore, a state in which a current flowing through the lead wire conducts to the first and the second electric conductor films is prevented. As a result, a stable detection result can be obtained. Specifically, an inner side insulator film is formed on the inner peripheral face of the first electric conductor film, an electrostatic capacity that is formed between the first electric conductor film and the center pole is detected, an outer side insulator film is formed on the outer peripheral face on the second electric conductor film, and a coil is wound around the outer peripheral face of the outer side insulator film to structure the voice coil bobbin.
In accordance with an embodiment, the second electric conductor film is grounded. According to this embodiment, for example, the effect of an AC current flowing through a coil included in the voice coil bobbin or the effect of an electromagnetic wave from the outside can be reduced by the second electric conductor film.
Further, in accordance with an embodiment, at least one of the first electric conductor film and the second electric conductor film is laminated. According to this embodiment, each layer of laminated electric conductor films cuts a circuit through which an eddy current flows and an eddy current is effectively confined in each of the films. Therefore, an eddy current can be suppressed. For example, it is preferable that the first electric conductor film is formed with a plurality of electric conductor films which are laminated.
Further, in accordance with an embodiment, at least one of the first electric conductor film and the second electric conductor film is formed with at least one of a plurality of slits and a plurality of holes. According to this embodiment, a loop of eddy current formed in the electric conductor film is cut by a plurality of slits or a plurality of holes and thus an eddy current can be suppressed. Specifically, it is preferable that one film of the first electric conductor film that is comprised of a plurality of electric conductor films is formed of a foil member and the foil member is provided with at least one of a plurality of slits and a plurality of holes for suppressing an eddy current in a substantially equal interval manner.
Other features and advantages of the invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawings that illustrate, by way of example, various features of embodiments of the invention.
Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures, in which:
An example of a speaker will be described in detail below with reference to the accompanying drawings.
A speaker in accordance with an embodiment is shown in
As shown in
The center pole 5 and the case 9 are connected to a housing (not shown) that is referred to as an enclosure and are grounded. The ring-shaped magnet 6 is magnetically attracted to a face of the flange 5b which faces the opening 9a so as to surround the main body 5a of the center pole 5 as its center. The substantially disk-shaped yoke 8 is magnetically attracted to a face of the magnet 6 which faces the opening 9a and thus the magnet 6 is disposed in a state that the magnet 6 is sandwiched between the yoke 8 and the flange 5b of the center pole 5. The magnet 7 whose shape is the same as the magnet 6 is disposed between the face of the flange 5b that faces the bottom part 9b of the case 9 and the bottom part 9b. The magnet 7 is disposed on the bottom part 9b such that the pole of the magnet 7 on the side abutting with the flange 5b is the same pole of the magnet 6 on the side abutting with the flange 5b. According to the structure described above, a stable magnetic flux loop (described below) is formed between the magnet 7, the yoke 8 and the center pole 5.
The substantially disk-shaped yoke 8 is disposed so as to be substantially perpendicular to the axis in the longitudinal direction of the cylindrical main body 5a of the center pole 5. The yoke 8 is magnetically attracted to the magnet 6 such that the inner peripheral face of the yoke 8 faces the outer peripheral face 5c of the main body 5a of the center pole 5 and an air gap is formed between the inner peripheral face of the yoke 8 and the outer peripheral face 5c. Further, the inner peripheral face of the substantially disk-shaped yoke 8 faces the main body 5a of the center pole 5 within the case 9 and the outer peripheral face of the yoke 8 is disposed to be positioned close to the inner wall face of the case 9.
The voice coil bobbin 4 comprises a tubular shaped bobbin 10 whose front end and rear end are opened and a coil 11 which is wound around the outer periphery of the bobbin 10. An electric conductor such as an enameled wire or a copper wire is preferably used as the coil 11 or another appropriate electric conductor may be used. The bobbin 10 is installed in the case 9 so as to be capable of sliding in a forward and backward direction (direction of the arrow “A” in
The frame 12 is bonded with an adhesive to the face of the yoke 8 which is exposed on the outer side of the case 9. Further, the frame 12 is bonded with a screw or an adhesive to the housing (not shown) and is grounded. The diaphragms 2, 3 are attached to the bobbin 10. The diaphragm 2 is a thin plate provided with a plurality of bent portions. One end of the diaphragm 2 is bonded to the outer peripheral face of the bobbin 10 and the other end of the diaphragm 2 is bonded to the frame 12 with an adhesive. The diaphragm 3 serves as a so-called cone paper. One end of the diaphragm 3 is connected to the outer peripheral face of the bobbin 10 and the other end of the diaphragm 3 is connected to the frame 12 through a joint 13. A center cap 14 is made of aluminum or the like and comprises a main body part which is formed in a dome shape and a flange part which is formed along the outer circumferential edge of the main body part. The flange part of the center cap 14 is bonded to the diaphragm 3 with an adhesive. Therefore, the opening 10a of the bobbin 10 is covered by the center cap 14.
As shown in
A detector 18, a converter 19 and a feedback circuit 20 are provided in the speaker 1. The detector 18 is a so-called capacitor that is comprised of the center pole 5 and an inner side copper plating 23 (see
As shown in
The pipe body 21, which serves the base of the voice coil bobbin 4, is structured by forming a roughly strip-shaped sheet 28 made of polyimide into a cylindrical shape as shown in
An inner side copper plating 23 is coated as shown in
As shown in
As described above, the inner side copper foil 22, the inner side copper plating 23 and the inner side resist 24 are successively laminated on the one face of the sheet 28, i.e., on the inner peripheral face 21a of the pipe body 21. The outer side copper foil 5, the outer side copper plating 26 and the outer side resist 27 are successively laminated on the other face of the sheet 28, i.e., on the outer peripheral face 21b of the pipe body 21. After that, both end portions in the longitudinal direction of the sheet 28 in
As described above, according to the speaker 1 having the structure shown in
However, in the speaker 1 in accordance with an embodiment of the present invention, since the outer side copper foil 25 and the outer side copper plating 26 are formed on the outer peripheral face 21b of the pipe body 21, an electric current flowing through the coil 11, an electromagnetic wave entering from the outside and the like can be blocked. Further, since the outer side resist 27 is formed between the outer side copper plating 26 and the coil 11, the outer side copper plating 26 and the coil 11 can be electrically insulated by the outer side resist 27. Therefore, an electric current flowing through the coil 11 may not conduct through the outer side copper plating 26 and the outer side copper foil 25. Further, since the outer side copper plating 26 is grounded, an electric current flowing in the coil 11 or an electromagnetic wave from the outside are absorbed by the outer side copper plating 26. In addition, since the inner side resist 24 is disposed between the outer side copper plating 26 and the outer peripheral face 5c of the main body 5a of the center pole 5, the relative permittivity of the capacitor which is formed by the outer side copper plating 26 and the main body 5a of the center pole 5 increases. In other words, the electrostatic capacity can be increased. Therefore, a real electrostatic capacity which is formed between the outer side copper plating 26 and the outer peripheral face 5c of the main body 5a of the center pole 5 can be accurately detected without being affected by a current flowing in the coil 11, an electromagnetic wave entering from the outside, or the like.
Further, when an electric conductor is moved in a constant magnetic field, an eddy current commonly flows in the surface of the electric conductor. However, in accordance with an embodiment, the inner side copper foil 22 and the inner side copper plating 23 are formed on the inner peripheral face 21a of the pipe body 21 and the copper film layer comprising the outer side copper foil 25 and the outer side copper plating 26 is formed on the outer peripheral face 21b of the pipe body 21. Therefore, a circuit where an eddy current flows is cut off and the current can be effectively confined in individual film layers and thus the eddy current can be suppressed. In addition, a plurality of holes 22a is formed in the inner side copper foil 22 that is a foil member in or over roughly the entire region and at a roughly equal interval and thus the circuit for the eddy current can be cut off by the holes 22a and the eddy current can be further suppressed by the holes 22a. Therefore, a real electrostatic capacity that is formed between the outer side copper plating 26 and the outer peripheral face 5c of the main body 5a of the center pole 5 can be further accurately detected without being affected by the eddy current.
The present invention has been described in detail using the embodiments, but the present invention is not limited to the embodiments described above and many modifications can be made without departing from the present invention. For example, as shown in
Further, in the embodiment described above, the inner side copper foil 22 in which a plurality of holes 22a is formed over the almost entire region in a substantially equal interval is used. However, the present invention is not limited to this embodiment. A pattern that combines the holes 22a and a plurality of slits 22b shown in
In the embodiment described above, a plurality of the holes 22a is formed in the inner side copper foil 22 which is a foil member. However, the present invention is not limited to this embodiment and similar holes as described above and similar slits to the slits 22b shown in
In the embodiment described above, a double (two-layer) copper film layer comprising of the inner side copper foil 22 and the inner side copper plating 23 is formed on the inner peripheral face 21a of the pipe body 21, and a double copper film layer comprising of the outer side copper foil 25 and the outer side copper plating 26 is formed on the outer peripheral face 21b of the pipe body 21. However, the present invention is not limited to this embodiment and three layers or four layers of copper film layer may be formed and the number of laminated layers may be appropriately changed.
In the embodiment described above, the inner side copper foil 22 is stuck on the inner peripheral face 21a of the pipe body 21 and, in addition, the inner side copper plating 23 is coated on the inner side copper foil 22, and further, the outer side copper foil 25 is stuck on the outer peripheral face 21b of the pipe body 21 and, in addition, the outer side copper plating 26 is coated on the outer side copper foil 25. Therefore, the copper film layers are formed on the inner peripheral face 21a and the outer peripheral face 21b of the pipe body 21, respectively. However, the copper film layer may be formed on each of the inner peripheral face 21a and the outer peripheral face 21b of the pipe body 21 by evaporating copper. In this manner, a method for forming the copper film layer can be changed appropriately.
In the embodiment described above, a coating process is used to form the inner side resist 24 on the inner side copper plating 23 and to form the outer side resist 27 on the outer side copper plating 26. However, the inner side resist 24 and the outer side resist 27 that are formed in a film shape may be stuck on the inner side copper plating 23 and the outer side copper plating 26 with an adhesive. As described above, the respective resists may be formed in a film-like manner and a method for forming the resist may be changed appropriately.
In the embodiment described above, the copper film layer is formed on the inner peripheral face 21a and the outer peripheral face 21b of the pipe body 21. However, the present invention is not limited to this embodiment. For example, an aluminum layer made of aluminum or an electro-conductive plastic layer may be formed on the inner peripheral face 21a and the outer peripheral face 21b of the pipe body 21. A nonmagnetic and electric conductor film may be formed on the inner peripheral face 21a and the outer peripheral face 21b of the pipe body 21 and the material of the film layer may be changed appropriately.
In the embodiment described above, the pipe body 21 is structured by using polyimide but its material is not limited to polyimide. For example, the material of the pipe body 21 may be paper or appropriately changed when the pipe body 21 is structured by using an insulator.
While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention.
The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-167530 | Jun 2005 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4727586 | Johnson | Feb 1988 | A |
| 4924858 | Katona | May 1990 | A |
| Number | Date | Country |
|---|---|---|
| 52-79644 | Jul 1977 | JP |
| 53-12319 | Feb 1978 | JP |
| 53-12320 | Feb 1978 | JP |
| 53-12321 | Feb 1978 | JP |
| 57014280 | Jan 1982 | JP |
| 08205285 | Aug 1996 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20060290481 A1 | Dec 2006 | US |
