JP2004056771A - Vibrating membrane for electro-acoustic transducer and electro-acoustic transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plane type electroacoustic transducer of a moving magnet type formed by a vibrating membrane having a thin film magnet magnet-landed to a thickness direction. <P>SOLUTION: The thin film magnet 12 is film-formed on a macromolecule film 11 such as a polyimide resin and the like by cobalt chromium and the like, and the vibrating membrane 10 formed by magnet-landing the thin film magnet 12 to the thickness direction is arranged in an air-core coil 20. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a diaphragm and an electro-acoustic transducer for an electro-acoustic transducer used for a speaker or a microphone. More specifically, the electro-acoustic transducer suitable for a flat speaker is thin and lightweight, while being a moving magnet type. The present invention relates to a vibrating film, an electro-acoustic transducer having the vibrating film, and a multi-point drive type electro-acoustic transducer in which a large number of the electro-acoustic transducers are arranged.
[0002]
[Prior art]
With the advent of liquid crystal displays and plasma displays in recent years, speakers that are sound output means have been required to be flat. That is, if the speaker, which is the sound output means, is still a cone type with respect to the flat type display, total flattening cannot be achieved.
[0003]
Recently, demands for flattening portable speakers have been increasing. Therefore, various companies have proposed various types of flat (thin) speakers, but in many cases, a flat coil is formed on a base material made of a polymer film as a vibrating film, and a permanent magnet is arranged so as to face the coil. I am trying to do it.
[0004]
[Problems to be solved by the invention]
As described above, the conventional planar speaker is a moving coil type, but to realize a moving magnet type planar speaker, the weight is equal to or less than the movable coil (printed coil), and the magnetic field generated by the drive coil is required. Therefore, a permanent magnet which does not demagnetize / demagnetize sufficiently against the magnetic field is required.
[0005]
Further, a permanent magnet for a moving magnet type flat speaker is required to have a high Curie temperature and a large energy product (BHmax) so as not to be easily demagnetized by temperature. A moving McNet type planar transducer capable of responding to the frequency domain has not reached the practical stage.
[0006]
[Means for Solving the Problems]
The present invention has been made in order to solve the above-mentioned problems, and a first invention of the present application is to provide an electroacoustic transducer that vibrates passively by an incoming sound wave or actively vibrates itself to generate a sound wave. In the dexterous diaphragm, a polymer film whose periphery is supported by a predetermined support, and a thin film magnet made of a permanent magnet material formed on at least one surface of a central portion of the polymer film excluding the periphery are provided. The thin film magnet is characterized in that it is magnetized in its thickness direction (vertical direction).
[0007]
The thin film magnet may be provided on one side of the polymer film, but is preferably provided on both sides in view of the vibration characteristics of the vibrating membrane. Alternatively, two polymer films each having a thin film magnet formed on one surface may be bonded to the other surface.
[0008]
In the present invention, the coercive force of the thin-film magnet is required to be sufficiently large with respect to the magnetic field generated by the drive coil in the case of a speaker application, and it is important that the magnetization direction is perpendicular to the film. For this thin film magnet, a perpendicular magnetic thin film made of cobalt chromium (CoCr) developed as a magnetic memory medium is optimal.
[0009]
A polyimide film having good heat resistance is suitable for the polymer film, and the film thickness is preferably 50 μm or less. Further, the thickness of the thin film magnet is determined depending on the relationship with the high coercive force while suppressing the increase in the movable mass thereof, and is generally preferably 0.1 mm or less.
[0010]
The thin film magnet is formed on a polymer film by, for example, a sputtering method.However, in order to prevent the thin film magnet from peeling off from the polymer film due to vibration or aging of the polymer film, the thin film magnet is formed on the polymer film. It is preferable to apply a coating film so as to cover the surface of the thin film magnet.
[0011]
The second invention of the present application relates to an electroacoustic transducer, wherein the vibrating membrane according to the first invention is arranged in an air-core coil such that the film surface is orthogonal to the axis of the air-core coil. . This electro-acoustic transducer is applicable to both a microphone and a speaker. In the case of a speaker, a particularly thin and lightweight flat speaker can be obtained.
[0012]
According to a preferred embodiment of the present invention, the air-core coil is formed of a conductor pattern (ultra-flat rectangular wire) such as copper foil formed on the periphery of the vibrating membrane. Since the flow is offset to the skin, the coil may have an apparently reduced cross-sectional area and may generate heat. To prevent this, it is preferable to make slits in the conductor pattern to make the air-core coil litz wire.
[0013]
In the electroacoustic transducer of the present invention, an annular yoke made of, for example, an iron-based soft magnetic material is arranged around the air-core coil in order to efficiently perform magnetic coupling between the air-core coil and the thin film magnet of the vibrating membrane. Is preferred.
[0014]
Further, the electro-acoustic transducer of the present invention is characterized in that the air-core coil is arranged at a position separated from the diaphragm by a predetermined height between the stationary position of the diaphragm and the maximum displacement position during vibration. . In this case, it is preferable that the air-core coil be arranged at a position where the rate of time change at which the magnetic flux of the thin-film magnet interlinks with the air-core coil is maximum.
[0015]
In actually assembling the electroacoustic transducer, if the air-core coil is made of a conductor pattern formed on the periphery of the vibrating membrane, both the front and back surfaces of the air-core coil are fixed and stationary by the support, and only the part having the thin film magnet vibrates It is possible. Further, a vibrating membrane edge is formed between the air-core coil and the thin-film magnet. According to the present invention, the thin-film magnet, the air-core coil and the vibrating membrane edge can be precisely formed on a polymer film as the vibrating membrane. It can be formed integrally in the positioned state.
[0016]
The present invention also includes a multi-point drive type electro-acoustic transducer (for example, a planar speaker) in which a plurality of the electro-acoustic transducers are arranged on a mother board of a predetermined size (for example, a business card size). . The present invention also includes the use as a pressure sensor.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged plan view showing one side of an electroacoustic transducer according to the present invention, which is divided into two parts for drawing, FIG. 2 is an enlarged sectional view thereof, and FIG. 3 is an explanatory view showing a terminal processing method of an air-core coil. It is.
[0018]
The electro-acoustic transducer 1 has, as a basic configuration, a vibrating membrane 10, an air-core coil 20 formed on the periphery of the vibrating membrane 10, and supports the vibrating membrane 10 via the air-core coil 20 so as to be able to vibrate. It has a support ring (diaphragm ring) 30 and an annular yoke 40 arranged around the air core coil 20.
[0019]
The vibration film 10 includes a polymer film 11 as a base material and a thin film magnet 12 formed on the polymer film 11. As the polymer film 11, a polyimide resin having good heat resistance and also being tough is preferably employed.
[0020]
It is preferable that the film thickness of the polymer film 11 be different for active use, for example, a speaker, which vibrates by itself and emits sound, and for passive use, for example, a microphone which vibrates by an incoming sound wave.
[0021]
As an example, in the case of active use, the thickness is preferably 50 μm or less, and for example, 12.5 μm, 25 μm, 50 μm, or the like may be appropriately selected. On the other hand, in the case of passive use, the film thickness is about 1/10 of the film thickness of active use, and in the case of both active / passive use, an intermediate film thickness is adopted. In this example, the diameter of the diaphragm 10 is about 10 mm.
[0022]
The peripheral edge of the polymer film 11 is supported by the support ring 30. In this example, a damper 111 having a corrugated cross section is provided near the inner peripheral side of the support ring 30 as a diaphragm edge. The damper 111 plays a role as an acoustic terminal of the diaphragm, and is designed in consideration of, for example, acoustic characteristics from a low band to a high band.
[0023]
The thin film magnet 12 is provided at a central portion of the polymer film 11. When the damper 111 is formed on the polymer film 11, the damper 111 is provided inside the damper 111. The damper 111 can be formed by hot pressing or the like.
[0024]
The thin film magnet 12 is formed on the polymer film 11 by, for example, a sputtering method. In the present invention, the thin film magnet 12 is made of cobalt chromium and is magnetized as a perpendicular magnetic thin film in its thickness direction (vertical direction).
[0025]
The thin film magnets 12 are preferably formed on both front and back surfaces of the polymer film 11, but two polymer films 11 are used, and after forming the thin film magnets 12 on one of the surfaces, the other surface is adhered to each other. May be combined.
[0026]
The thin film magnet 12 preferably has a thickness of 100 μm or less per one surface of the polymer film 11. This film thickness may be appropriately selected according to the permanent magnet material used, the film forming method, and the like. In some cases, the polymer film 11 may be formed only on one side instead of both sides.
[0027]
In order to prevent the thin film magnet 12 from peeling off from the polymer film 11 due to vibration or aging of the polymer film 11, a coating film (shown in the drawing) is formed on the polymer film 11 so as to cover the surface of the thin film magnet 12. (Omitted) is preferable.
[0028]
The air core coil 20 is formed along the periphery of the polymer film 11 concentrically with respect to the thin film magnet 12. In this example, the air-core coil 20 is made of, for example, a conductor pattern of copper foil, and includes, for example, coil members 21, 22;
[0029]
That is, the coil members 21 and 22 for two turns are formed concentrically on the upper surface side of the polymer film 11, and the coil members 24 and 25 for the remaining two turns are also concentrically formed on the lower surface side of the polymer film 11. Is formed.
[0030]
As shown in FIG. 3A, the terminal processing of the air-core coil 20 may be performed by connecting the respective coil members in series and extracting the current-carrying terminals 20a and 20b from both ends of the coil. As shown in (b), each coil member may be connected in parallel to the energizing terminals 20a and 20b.
[0031]
In this example, each of the coil members 21, 22; 24, 25 is formed as a super-flat rectangular wire having a thickness of 0.1 mm and a width of 0.8 mm. The DC resistance of each of the coil members 21, 22; 24, 25 is preferably as small as possible (eg, 0.1Ω or less). However, when the frequency of the current flowing through the air-core coil 20 increases, the current flows to the outer skin. For this reason, the coil cross-sectional area may be apparently reduced and the coil may generate heat.
[0032]
In order to prevent this, a litz wire method is adopted for the air-core coil 20, and in this example, a V-shaped slit G is formed in each of the coil members 21, 22; Divided. As a modification, the air-core coil 20 may be formed by arranging a conductive wire on the vibration film 10 in a loop coil shape.
[0033]
The support ring 30 is entirely made of a non-magnetic material such as a synthetic resin. In this example, the support ring 30 includes two washers 31 and 32 stacked on the upper coil members 21 and 22 of the vibration film 10. And two washers 33 and 34 which are laminated on the lower coil members 24 and 25 of the diaphragm 10. Note that each of the washers 31, 32 and the washers 33, 34 may be integrated into one sheet.
[0034]
The yoke 40 is a cylindrical body made of, for example, a soft magnetic material such as an iron-based material, and is disposed on the outer peripheral surface side of the support ring 30 in order to efficiently magnetically couple the air core coil 20 and the thin film magnet 12. .
[0035]
When the electroacoustic transducer 1 is used as a speaker, a drive current of an audio signal is supplied to the air core coil 20. As a result, the magnetic flux generated from the air core coil 20 acts on the thin film magnet 12, and the vibration film 10 vibrates. That is, it operates as a moving magnet type.
[0036]
FIG. 4 shows an example in which a plurality of (for example, 12) electro-acoustic transducers 1 are allocated to a business card-sized mother board M to provide a multi-point driven planar speaker. Incidentally, in this example, the electroacoustic transducer 1 has a diameter of about 10 mm and a thickness of about 4 mm.
[0037]
Next, an example of a manufacturing process of the above-described electroacoustic transducer 1 will be described with reference to FIG. First, as shown in FIG. 5A, a circular film made of, for example, a block-copolymerized polyimide film having a thickness of 5 μm is used as the polymer film 11, and a cobalt chromium film is formed on a substantially central portion of one surface 11a by a sputtering method or the like. The thin film magnet 12 is formed to a thickness of about 50 to 60 μm.
[0038]
Next, as shown in FIG. 5B, a conductor pattern 20A of a copper foil is formed concentrically around the thin film magnet 12 around one surface 11a of the polymer film 11 by, for example, a vapor deposition method. In some cases, the conductor pattern 20 </ b> A made of a copper foil may be attached to the polymer film 11.
[0039]
Then, as shown in FIG. 5C, a photoresist (not shown) is applied on the conductor pattern 20A of the copper foil, exposed and developed, and the coil member of the air-core coil 20 is placed around the polymer film 11. Form for several turns.
[0040]
The number of turns is arbitrary, but in this example, coil members 21, 22, 23 for three turns are formed. Thereafter, the terminal processing of the coil members 21, 22, and 23 is performed according to any of the previously described FIGS. 3A and 3B.
[0041]
As shown in FIG. 5D, a predetermined number of slits G are concentrically formed in each of the coil members 21, 22, and 23 by an etching process in order to suppress the generation of the eddy current, if necessary. Form and litz wire.
[0042]
In this way, two films each having the thin film magnet 12 and the air core coil 20 formed on the polymer film 11 are produced, and as shown in FIG. 5 (e), the back surfaces 11b, The vibration films 10 are obtained by laminating the layers 11b with each other via, for example, a predetermined adhesive.
[0043]
Then, after the thin film magnets 12 are magnetized in the film thickness direction (vertical direction), the support ring 30 is attached to the vibration film 10 and the yoke 40 is arranged on the outer periphery thereof as described with reference to FIG.
[0044]
In the case where the damper (vibrating film edge) 111 is formed by, for example, hot pressing, it is preferable to form the damper 111 before forming the thin film magnet 12, but as shown in FIG. After laminating the films, the dampers 111 may be formed.
[0045]
Thus, the electro-acoustic transducer 1 of the present invention is obtained. Next, an example of manufacturing a planar speaker will be described with reference to FIG.
[0046]
As shown in FIG. 6, the thin film magnet 12 (thickness) is formed at a plurality of locations (six locations in this example) on a mother film A of a predetermined size made of, for example, a 5 μm-thick polyimide film according to the production method described with reference to FIG. (About 50 to 60 μm) and the air-core coil 20. At the time of coil formation, each air core coil 20 is connected in series with a crossover W, and energization terminals Ta and Tb are formed at both ends of the crossover W.
[0047]
Separately, a yoke plate B and a holding plate C having substantially the same size as the mother film A are prepared, and a through hole BH slightly larger than the outer diameter of each air core coil 20 is formed in each yoke plate B. Further, a through hole CH having a diameter slightly smaller than the inner diameter of each air core coil 20 is formed in the holding plate C.
[0048]
The yoke plate B is made of a soft magnetic material, and corresponds to the yoke 40 described above. The pressing plate C is for allowing only the thin film magnet 12 of the mother film A to vibrate and for fixing and resting other portions including the air core coil 20. The pressing plate C is a synthetic resin substrate having a predetermined hardness. (Magnetic substrate). This pressing plate C corresponds to the above-described support ring 30.
[0049]
Then, as shown in FIG. 7A, a yoke plate B and a pressing plate C are bonded to each other on the mother film A via a predetermined adhesive to obtain a laminate D. As shown in FIG. 7B, a pair (one set) of the laminates D is prepared and bonded as back to back.
[0050]
In this way, a planar speaker including a plurality of electroacoustic transducers 1 is obtained, and the electroacoustic transducer 1 can be used as a microphone unit. That is, when the vibrating membrane 10 vibrates due to an incoming sound wave, the magnetic flux acting on the air-core coil 20 changes, so that a voltage is induced in the air-core coil 20, and the induced voltage is amplified and taken out, so that an audio signal is obtained. Obtainable.
[0051]
Separately, a magnetoresistive effect type magnetic response element (MR element) made of permalloy or the like is disposed directly below the thin film magnet 12 through a gap of about 10 μm to take out the vibration of the vibrating film as an electric signal. You can also.
[0052]
The present invention also includes the electroacoustic transducer 1A of the embodiment shown in FIG. FIG. 8 shows an example, and the electroacoustic transducer 1A is not limited to this. Also in this electroacoustic transducer 1A, the vibrating membrane 10 having the thin film magnets 12, 12 is provided on both surfaces of the polymer film 11, and the peripheral edge thereof is sandwiched by a pair of upper and lower non-magnetic support rings 301, 302. It is supported.
[0053]
Air-core coils 201 and 202 are arranged on both sides of the periphery of the vibration film 10. In this electroacoustic transducer 1 </ b> A, the air-core coils 201 and 202 are not on the same plane as the vibration film 10 but are vibrated. It is located at a predetermined height away from the membrane 10.
[0054]
That is, the air-core coils 201 and 202 are located in a plane parallel to the diaphragm 10 at a height position between the stationary position of the diaphragm 10 and the maximum displacement position during vibration (the position shown by the dashed line). Supported by the support rings 301 and 302 as described above.
[0055]
When this electroacoustic transducer 1A is used for a microphone, the change in the distribution of the magnetic flux of the thin film magnets 12 due to the external sound pressure of the diaphragm 10 is caused by the air-core coil 201 serving as a detection coil disposed on the periphery of the diaphragm 10. , 202, that is, as a time induced voltage e.
[0056]
Here, assuming that the position of the vibration film 10 in the vibration direction is x, and the amount of magnetic flux of the thin film magnets 12, 12 to the air-core coils 201, 202 is λ, the velocity induced voltage e is e = (δλ / Δx) · (dx / dt). Among them, the velocity component (dx / dt) is zero at the maximum displacement position, and is maximum at zero displacement (stationary position).
[0057]
On the other hand, the ratio of the magnetic flux linked to the air-core coils 201, 202 of the thin film magnets 12, 12 at the position x in the vibration direction is the change of the permeance distribution from the thin film magnets 12, 12 with respect to the position of the permeance distribution when viewed three-dimensionally outward. Equivalent to percentage. The product of the two determines the speed induced voltage e. Therefore, the position where the air-core coils 201 and 202 are arranged is preferably a position where the speed induced voltage e is maximum.
[0058]
Instead of the thin film magnets 12, a spiral coil (not shown) may be arranged on the polymer film 11, and a direct current may flow through the coil to act as an electromagnet.
[0059]
In the embodiment shown in FIG. 8, two air core coils 201 and 202 are used in the above example, but in some cases, only one of the air core coils may be used. Alternatively, two air-core coils may be arranged on each side of the vibrating membrane, two each, for a total of four.
[0060]
【The invention's effect】
As described above, according to the present invention, a thin film magnet is formed on a polymer film, and a vibrating film formed by magnetizing the thin film magnet in the thickness direction (vertical direction) is disposed in the air-core coil. Accordingly, a moving coil type planar electroacoustic transducer having performance equal to or higher than that of the moving coil type can be obtained.
[0061]
In addition, by placing the air-core coil on the plane parallel to the diaphragm at a predetermined height between the rest position and the maximum displacement position of the diaphragm, instead of being on the same plane as the diaphragm, microphone applications In this case, a large detection voltage can be obtained, and in the case of a speaker application, the diaphragm can be driven more efficiently.
[Brief description of the drawings]
FIG. 1 is an enlarged plan view showing one side of an electro-acoustic transducer according to the present invention as divided into two parts for drawing.
FIG. 2 is an enlarged sectional view of the electroacoustic transducer.
FIG. 3 is an explanatory view showing two examples of terminal processing of an air core coil provided in the electroacoustic transducer.
FIG. 4 is a schematic diagram showing a multipoint drive type planar speaker in which a plurality of the electroacoustic transducers are arranged on a motherboard.
FIG. 5 is an explanatory view showing a manufacturing process of the electroacoustic transducer.
FIG. 6 is an explanatory view showing a manufacturing process of the multipoint drive type planar speaker.
FIG. 7 is an explanatory view showing a manufacturing process of the multipoint drive type planar speaker.
FIG. 8 is a schematic sectional view showing another embodiment of the electro-acoustic transducer according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electroacoustic transducer 10 Vibration film 11 Polymer film 12 Thin film magnet 20, 201, 202 Air core coils 21 to 25 Coil members 30, 301, 302 Support ring 40 Yoke A Mother film B Yoke plate C Holding plate D Stacked body BH , CH through hole

Claims (13)

In the vibrating membrane for an electroacoustic transducer, which vibrates passively by arriving sound waves or actively vibrates itself to generate sound waves,
A polymer film whose periphery is supported by a predetermined support, and a thin film magnet made of a permanent magnet material formed on at least one surface of a central portion of the polymer film excluding the periphery, wherein the thin film magnet is provided. A vibrating membrane for an electroacoustic transducer, which is magnetized in the thickness direction. The vibrating membrane for an electroacoustic transducer according to claim 1, wherein the thin film magnet is provided on both surfaces of the polymer film. 2. The vibrating membrane for an electroacoustic transducer according to claim 1, wherein two of the polymer films each having the thin film magnet formed on one surface are bonded to each other on the other surface. 3. The vibrating membrane for an electroacoustic transducer according to any one of claims 1 to 3, further comprising a coating film formed on the polymer film so as to cover a surface of the thin film magnet. 5. The vibrating membrane for an electroacoustic transducer according to claim 1, wherein the thin film magnet is made of cobalt chromium. The vibration film for an electroacoustic transducer according to any one of claims 1 to 5, wherein the vibration surface is arranged in the air-core coil such that the film surface is orthogonal to the axis of the air-core coil. Electroacoustic transducer. The electroacoustic transducer according to claim 6, wherein the air-core coil is formed of a conductor pattern formed concentrically with the thin-film magnet on the periphery of the vibrating membrane. The electroacoustic transducer according to claim 7, wherein the conductor pattern is formed into a litz wire. The electroacoustic transducer according to any one of claims 6 to 8, further comprising an annular yoke made of a magnetic material disposed around the air core coil. The electro-acoustic transducer according to claim 7 or 8, wherein both the front and back surfaces of the air-core coil are fixed and stationary by a support, and only the thin film magnet can vibrate. The electroacoustic transducer according to claim 10, wherein a vibrating membrane edge is formed between the air-core coil and the thin-film magnet. 12. The air-core coil according to claim 6, 8, 9 or 11, wherein the air-core coil is disposed at a position separated from the vibration film by a predetermined height between a position of the vibration film at rest and a maximum displacement position during vibration. An electroacoustic transducer as described. A multi-point drive type electro-acoustic transducer comprising a plurality of electro-acoustic transducers according to any one of claims 6 to 11 arranged on a mother board of a predetermined size.

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