JP3725528B2 - Flat speaker - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flat speaker having a flat diaphragm.
[0002]
[Prior art]
FIG. 9 shows an example of a conventional flat speaker. In the figure, 10 is an iron plate (ferromagnetic metal plate), a yoke in which a flat plate portion 10a and a peripheral wall portion 10b are integrally formed, and 12 is a number of permanent magnets attached to one side of the yoke flat plate portion 10a with their magnetic axes vertically upright. , 14 are diaphragms. The permanent magnet 12 is attached to the yoke flat plate portion 10a with a predetermined interval so that the polarities of the magnetic poles are opposite to each other. The diaphragm 14 is provided with a voice coil 18 corresponding to each permanent magnet 12 on one side (or both sides) of the insulating sheet 16.
[0003]
Each voice coil 18 is formed so as to surround a region facing the magnetic pole of the permanent magnet 12. All the voice coils 18 are wound so that currents in the same direction flow in adjacent sides of adjacent voice coils. Each voice coil 18 is preferably formed in a plane spiral shape to improve acoustic conversion efficiency and design freedom as much as possible. The peripheral portion of the vibration plate 14 is attached to the edge of the yoke peripheral wall portion 10b via a holding frame 20 having spring elasticity, whereby the vibration plate 14 maintains a predetermined gap from the magnetic pole surface of the permanent magnet 12. So that it is held.
[0004]
An air hole 22 is formed in the yoke flat plate portion 10a for relaxing fluctuations in air pressure caused by vibration of the diaphragm 14. A buffer sheet 24 that prevents the diaphragm 14 from colliding with the magnetic pole surface of the permanent magnet 12 due to vibration is joined to the upper surface of the permanent magnet 12. The flat speaker configured as described above is disclosed in Patent Document 1, for example.
[0005]
[Patent Document 1]
Republished Patent Publication WO00-078095 [0006]
[Problems to be solved by the invention]
Diaphragm of flat speaker, because its only a peripheral portion held by the holding frame, the larger signal of the low frequency range of the amplitude of the lowest resonance frequency f ₀ near is input, the lowest resonance frequency f ₀ near the The amplitude of the diaphragm increases, and the diaphragm easily collides with the buffer sheet and easily generates abnormal noise. The generation of abnormal noise is particularly noticeable when the diaphragm vibrates in a mode such as the two-point difference line of FIG. 10 (A) or (B). (A) is the case where the diaphragm vibrates in the primary vibration mode, and (B) is the case where it vibrates in the secondary vibration mode. The amplitude of the diaphragm is greatest in the primary vibration mode and decreases in the order of the secondary vibration mode and the tertiary vibration mode. For this reason, in a full range flat speaker, abnormal noise is likely to occur during reproduction in the low sound range, and it has been difficult to increase the value of input resistance.
[0007]
In addition, the flat speaker needs to have the gap between the diaphragm and the magnetic pole surface of the permanent magnet set to a predetermined size over the entire surface. For this reason, conventionally, when the holding frame attached to the periphery of the diaphragm is attached to the edge of the yoke peripheral wall, the gap is adjusted to a predetermined size. It was difficult to adjust.
[0008]
A first object of the present invention is to provide a flat speaker in which abnormal noise is prevented from occurring.
[0009]
A second object of the present invention is to provide a flat speaker in which the gap between the diaphragm and the magnetic pole surface of the permanent magnet can be easily adjusted to a predetermined size.
[0010]
[Means for Solving the Problems]
In order to achieve this object, the present invention provides a yoke having a flat plate portion, a large number of permanent magnets attached to the flat plate portion of the yoke, and voice coils corresponding to the permanent magnets on one or both sides of an insulating sheet. A planar speaker comprising a diaphragm and a holding frame that holds a peripheral portion of the diaphragm so that a predetermined gap is formed between the diaphragm and the magnetic pole surface of the permanent magnet. An amplitude that relatively vibrates with a larger amplitude than other locations, but with an amplitude that does not reach the magnetic pole surface level of the permanent magnet at that location, is allowed, but an amplitude that suppresses vibration with an amplitude reaching the magnetic pole surface level A suppression member is provided.
[0011]
In the flat speaker of the present invention, it is preferable that the amplitude suppressing member is provided at at least one of the positions corresponding to the center of the antinode or the vicinity of the antinode of the lower order vibration mode below the third order vibration mode of the diaphragm.
[0012]
In the flat speaker of the present invention, it is preferable that the amplitude suppressing member is configured to support the stationary diaphragm with a predetermined gap between it and the magnetic pole surface of the permanent magnet.
[0013]
In the flat speaker of the present invention, the amplitude suppressing member includes a damper having a concentric circular waveform and a peripheral portion fixed to the yoke, one end side fixed to the central portion of the damper, and the other end side being a diaphragm. It can comprise with the support member fixed to.
[0014]
In this case, the support member may be a trumpet member or a cylindrical member in order to increase the support area of the diaphragm and reduce the weight.
[0015]
In the flat speaker of the present invention, the amplitude suppressing member can be composed of a solid block fixed to the yoke and an elastic body mounted on the solid block so as to support the diaphragm.
[0016]
In this case, the solid block may be the same as many permanent magnets attached to the yoke.
[0017]
In the flat speaker of the present invention, the amplitude suppression member can be configured by an electromagnetic braking mechanism.
[0018]
In this case, the electromagnetic braking mechanism was attached to the yoke so as to apply a radial magnetic flux to the movable coil, and a movable coil attached to the diaphragm via a support member so that the central axis is directed in the vibration direction. It can comprise with what has a magnet.
[0019]
In this case, it is preferable that the support member is supported by the yoke via a damper.
[0020]
In the flat speaker of the present invention, the amplitude suppressing member can be composed of a first magnet attached to the yoke and a second magnet attached to the diaphragm so that the same polarity as this magnet faces. .
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0022]
Embodiment 1 FIG. 1 shows an embodiment of the present invention. In FIG. 1, 10 is a yoke in which a peripheral wall portion 10b is integrally formed around a flat plate portion 10a, 12 is a permanent magnet, 14 is a diaphragm provided with a voice coil 18 on one side (or both sides) of an insulating sheet 16, and 20 is A holding frame 22 is an air hole.
[0023]
The feature of this flat speaker is that an opening 26 is formed in the central portion of the flat plate portion 10a of the yoke, and an amplitude suppression member 28 that supports the central portion of the diaphragm 14 is attached to the periphery of the opening portion 26. .
[0024]
The amplitude suppressing member 28 is obtained by fixing a trumpet-shaped support member 32 to the center of a disk-shaped damper 30 having a concentric circular waveform by bonding or the like. The damper 30 may be manufactured by thermoforming a sheet in which a cloth is impregnated with a thermosetting resin such as a phenol resin. The support member 32 is desirably as light as possible and may be formed of hard paper or resin foam. The peripheral portion of the damper 30 is fixed to the edge of the opening 26 of the yoke 10 by bonding or the like, and the front end edge of the support member 32 is fixed to the diaphragm 14 by bonding or the like.
[0025]
In principle, permanent magnets and voice coils are not provided in the region where the amplitude suppressing member 28 is provided. However, the region supported by the support member 32 of the diaphragm 14 may be provided with a voice coil or a rigidity imparting member having rigidity equivalent to that of the voice coil. This is to make the rigidity of the region of the diaphragm 14 supported by the support member 32 substantially the same as the rigidity of the other regions.
[0026]
In this embodiment, the amplitude suppression member 28 supports the central portion of the diaphragm 14, that is, the diaphragm 14 becomes the center of vibration when the diaphragm 14 vibrates in the primary vibration mode as shown in FIG. It is provided to support the part. When the vibration suppression member 28 vibrates with an amplitude that does not reach the magnetic pole surface level of the permanent magnet 12, the damper 30 elastically deforms to follow the vibration and does not hinder the vibration. On the other hand, if an attempt is made to vibrate with a large amplitude such that the central portion of the diaphragm 14 reaches the magnetic pole surface level of the permanent magnet 12, the amount of elastic deformation of the damper 30 reaches a limit, and the amplitude of the diaphragm 14 is suppressed to a certain limit or less. . Therefore, according to the above configuration, the diaphragm 14 can be prevented from colliding with the magnetic pole surface of the permanent magnet 12, and the generation of abnormal noise can be prevented.
[0027]
Further, since the amplitude suppressing member 28 supports the diaphragm 14 not by a point but by a surface (by an annular tip portion of the trumpet-like support member 32), the amplitude suppressing member 28 also has an effect of suppressing the inclination of the diaphragm 14. For this reason, for example, when the diaphragm 14 tries to vibrate in the secondary vibration mode as shown in FIG. 10B, it works to suppress the vibration, and as a result, the amplitude of the secondary vibration mode can be suppressed to a small value. Therefore, the amplitude suppressing member 28 configured as described above can prevent the vibration plate 14 from colliding with the magnetic pole surface of the permanent magnet 12 even when a secondary vibration mode is generated in the vibration plate. Can be prevented.
[0028]
In addition, since this flat speaker has a structure in which the central portion of the diaphragm 14 is supported by the amplitude suppressing member 28, the size of the gap between the diaphragm 14 and the magnetic pole surface of the permanent magnet 12 is set to the peripheral holding frame 20. It can be set by both of the amplitude suppression members 28 in the central portion. For this reason, it is easy to adjust the gap size to a predetermined size over the entire surface during assembly, and a flat speaker with high accuracy can be obtained.
[0029]
In the embodiment of FIG. 1, the amplitude suppression member 28 is provided so as to support a portion that becomes the center of the vibration antinode when the diaphragm 14 vibrates in the primary vibration mode. You may provide so that the board 14 may support the part which shifted | deviated slightly from the center of the antinode of vibration when vibrating in the primary vibration mode. This has the advantage that the resonance phenomenon in the primary vibration mode of the diaphragm can be suppressed.
[0030]
2A to 2C show other examples of positions where the amplitude suppression member 28 is provided. The broken line indicates the peak of the vibration mode of the diaphragm 14. (A) is a case where the diaphragm 14 is elliptical, and is provided with amplitude suppression members 28 at both the center of the antinode of the primary vibration mode and the center of the antinode of the secondary vibration mode. Even if the vibration suppressing member 28 is provided at only two locations slightly closer to the center than the two antinode centers in the secondary vibration mode, the predetermined effect can be obtained. When the diaphragm 14 is elliptical, the antinode of the secondary vibration mode may appear in an elliptical shape as indicated by the broken line in FIG. For this reason, (B) is provided with amplitude suppressing members 28 at four locations in the vicinity of the intersection of the elliptical major axis, minor axis and antinode. (C) shows a case where the diaphragm 14 is rectangular, and the amplitude suppressing member 28 is provided at a position slightly deviated from the center of the antinode of the primary vibration mode and a position slightly deviated from the center of the antinode of the secondary vibration mode. Thus, the position where the amplitude suppressing member is provided can be appropriately selected according to the size and shape of the flat speaker. This also applies to the following embodiments.
[0031]
Embodiment 2 FIG. 3 shows another embodiment of the present invention. This flat speaker is composed of a solid block 34 fixed to the central portion of the yoke flat plate portion 10a by adhesion or the like, and an elastic member 36 attached to the solid block 34 so as to support the diaphragm 14, and the amplitude suppressing member 28. Is configured. The elastic body 36 is joined to the solid block 34 by adhesion or the like. The elastic body 36 is preferably joined to the diaphragm 14, but it may be simply in contact. As the solid block 34, the same one as the permanent magnet 12 may be used, or a metal or plastic block may be used. As the elastic body 36, silicone gel, rubber, foam, a viscous resin-impregnated nonwoven fabric, or the like can be used.
[0032]
With the configuration as shown in FIG. 3, when the central portion of the diaphragm 14 vibrates with a small amplitude that does not reach the level of the magnetic pole surface of the permanent magnet 12, the repulsive force of the elastic body 36 is small and vibration is not hindered. On the other hand, when an attempt is made to vibrate with a large amplitude such that the central portion of the diaphragm 14 reaches the magnetic pole surface level of the permanent magnet 12, the repulsive force of the elastic body 36 increases and the amplitude of the diaphragm 14 is suppressed to a certain limit or less. . Therefore, the diaphragm 14 can be prevented from colliding with the magnetic pole surface of the permanent magnet 12, and abnormal noise can be prevented. Silicone rubber or the like having a hardness of 0 has a great effect of damping large amplitude vibrations of the diaphragm 14.
[0033]
Also in this embodiment, the size of the gap between the diaphragm 14 and the magnetic pole surface of the permanent magnet 12 can be set by both the peripheral holding frame 20 and the central amplitude suppressing member 28. For this reason, it is easy to adjust the gap size to a predetermined size over the entire surface during assembly, and a flat speaker with high accuracy can be obtained.
[0034]
The elastic body 36 may be provided so as not to contact the diaphragm 14 in a stationary state. However, in such a configuration, the amplitude suppressing member has no effect of setting the gap between the diaphragm and the magnetic pole surface of the permanent magnet to a predetermined size.
[0035]
Since the configuration other than the above is the same as that of the first embodiment, the same portions are denoted by the same reference numerals and description thereof is omitted.
[0036]
[Third Embodiment] FIGS. 4 to 6 show still another embodiment of the present invention. 4 to 6, the same parts as those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted. This flat speaker is provided with electromagnetic braking mechanisms 38A and 38B as amplitude suppression members at locations corresponding to the center of the antinode of the primary vibration mode and the vicinity of the antinode of the secondary vibration mode.
[0037]
As shown in FIG. 5, the electromagnetic braking mechanism 38A in the central portion includes a movable coil 42 attached to the diaphragm 14 via a support member 40 so that the central axis is directed in the vibration direction, and a magnetic circuit member 44 to the yoke 10. It has the magnet 46 attached via.
[0038]
The support member 40 of the movable coil 42 is formed in a trumpet shape on the side fixed to the diaphragm 14 and formed in a cylindrical shape on the free end side. The movable coil 42 is wound once or a plurality of times around the outer periphery of the cylindrical portion of the support member 40, and both terminals are short-circuited in order to effectively perform braking. In the case of a single roll, the support member 40 can be shared by using a lightweight conductive member such as aluminum. Furthermore, when a part of the movable coil is configured as an open circuit so that an audio signal flows, the electroacoustic conversion efficiency can be improved while applying electromagnetic braking with the movable coil in a short-circuited state. The support member 40 is held by a damper 48 at an intermediate portion in the axial direction. The damper 48 is an elastic member having a concentric waveform, and is the same as the damper 30 used in the first embodiment. The periphery of the damper 48 is fixed to the yoke flat plate portion 10a.
[0039]
A cylindrical portion 10c is formed outwardly at the central portion of the yoke flat plate portion 10a, and the magnetic circuit member 44 is fixed to the yoke flat plate portion 10a in a state of being fitted to the outer periphery of the cylindrical portion 10c. The magnetic circuit member 44 is made of the same ferromagnetic material as that of the yoke 10. A cap-shaped convex portion 44a is formed at the center of the magnetic circuit member 44, and the magnet 46 is positioned in the cylindrical portion of the support member 40 in a state of being fixed to the top of the cap-shaped convex portion 44a. The magnet 46, the yoke cylindrical portion 10c, and the magnetic circuit member 44 constitute a magnetic circuit, and the movable coil 42 is disposed in the gap between the magnet 46 and the yoke cylindrical portion 10c of this magnetic circuit. As a result, a radial magnetic flux is applied to the movable coil 42, and braking is applied when the movable coil 42 vibrates together with the diaphragm 14. The electromagnetic braking mechanism 38A is capable of obtaining a more reliable amplitude suppression action because braking by electromagnetic force and braking by the damper 48 are applied to the large amplitude vibration of the diaphragm 14. 5B shows an example in which the magnet 46 is a quadrangle, the shape of the magnet 46 may be other shapes such as a circle and a cylinder.
[0040]
Next, the electromagnetic braking mechanisms 38B provided on both sides have a structure as shown in FIG. That is, the movable coil 42 attached to the vibration plate 14 via the support member 40 is located in the opening formed in the yoke flat plate portion 10a. The support member 40 has a stepped cylindrical shape with a large diameter on the vibration plate 14 side, and the stepped portion is held by a damper 48. Four magnets 46 are attached at 90 ° intervals to the outer edge of the opening of the yoke flat plate portion 10a. A magnetic circuit member 44 is attached to the surface of the magnet 46 opposite to the yoke flat plate portion 10a. At the center of the magnetic circuit member 44, a cap-shaped convex portion 44a having an air hole at the top is formed. The movable coil 42 is disposed in an annular gap between the cap-shaped convex portion 44a and the inner surface of the opening of the yoke flat plate portion 10a. Even with such a structure, the same amplitude suppressing action as that of the central electromagnetic braking mechanism 38A can be obtained. Although FIG. 6B shows the case where four quadrangular magnets 46 are used, the shape of the magnet 46 is not limited to this, and may be, for example, one donut-shaped magnet.
[0041]
FIG. 7 shows another embodiment of the electromagnetic braking mechanism. This electromagnetic braking mechanism 38 also has a movable coil 42 attached to the diaphragm 14 via a cylindrical support member 40, and the axially intermediate portion of the support member 40 is held by a damper 48 in FIGS. This is the same as the electromagnetic braking mechanisms 38A and 38B. The electromagnetic braking mechanism 38 is different from the electromagnetic braking mechanisms 38A and 38B described above in that an annular recess 10d is formed in the yoke flat plate portion 10a, and one magnetic pole surface of the magnet 46 is joined to the bottom surface of the annular recess 10d. The inner peripheral cylindrical portion 10e of the annular recess 10d is positioned inside the support member 40, and an annular plate 50 made of a ferromagnetic material is joined to the other magnetic pole surface of the magnet 46. This is because the surface and the outer peripheral surface of the inner peripheral cylindrical portion 10e are opposed to each other with the movable coil 42 interposed therebetween. Even with such a structure, the same amplitude suppressing action as that of the electromagnetic braking mechanisms 38A and 38B can be obtained. Note that the upper end of the inner circumferential cylindrical portion 10e is opened as an air hole. If a light and highly rigid conductor such as aluminum is used for the support member 40, the support member 40 can have a function as a movable coil, and the number of parts can be reduced.
[0042]
Embodiment 4 FIG. 8 shows still another embodiment of the present invention. In this flat speaker, a first permanent magnet 52 is installed at the central portion of the yoke flat plate portion 10a, and the second permanent magnet is disposed so that the magnetic pole surface having the same polarity as the permanent magnet 52 faces the central portion of the diaphragm 14. 54, and the diaphragm 14 is prevented from colliding with the magnetic pole surface of the permanent magnet 12 due to the repulsive force of the permanent magnets 52 and 54. Since the configuration other than the above is the same as that of the flat speaker of FIG. 1, the same portions are denoted by the same reference numerals and description thereof is omitted. The first permanent magnet 52 is preferably the same as that of the other permanent magnets 12, but a different one can be used.
[0043]
As described above, in the description of the embodiment of the present invention, as the amplitude suppressing member 28, (1) a case where the trumpet-like support member 32 is attached to the damper 30, or (2) a case where the electromagnetic braking mechanism 38 is provided. , (3) The case where the repulsive force is used with the same polarity of the magnet facing each other, (4) The case where the elastic body is used, etc. are shown, but these may be provided in one place One type may be provided at a plurality of locations. A plurality of types can be provided at a plurality of locations.
[0044]
【The invention's effect】
As described above, according to the present invention, the vibration suppressing member is provided at a portion having a relatively larger amplitude than the other portions of the diaphragm so as to suppress the vibration of the diaphragm with a large amplitude. Further, it is possible to prevent the diaphragm from colliding with the magnetic pole surface of the permanent magnet, and it is possible to obtain a flat speaker with good sound quality with less noise. In addition, by supporting the diaphragm with the amplitude suppressing member, the gap between the diaphragm and the magnetic pole surface of the permanent magnet is made to have a predetermined size as compared with the case where only the periphery of the diaphragm is held by the holding frame. Is easy.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a flat speaker according to the present invention.
FIGS. 2A to 2D are explanatory views illustrating locations where an amplitude suppression member is installed in a flat speaker according to the present invention.
FIG. 3 is a cross-sectional view showing another embodiment of a flat speaker according to the present invention.
4A and 4B show still another embodiment of the flat speaker according to the present invention, in which FIG. 4A is a plan view with a diaphragm removed, FIG. 4B is a cross-sectional view along line BB in FIG. ) Is a bottom view, and FIG.
5A and 5B are cross-sectional views and a bottom view, respectively, showing an electromagnetic braking mechanism at the center of the flat speaker of FIG.
6A and 6B show electromagnetic braking mechanisms on both sides of the flat speaker of FIG. 4, in which FIG. 6A is a cross-sectional view, and FIG.
FIG. 7 is a cross-sectional view showing another example of an electromagnetic braking mechanism used in the flat speaker of the present invention.
FIG. 8 is a cross-sectional view showing still another embodiment of the flat speaker according to the present invention.
FIG. 9 is a cross-sectional view showing a conventional flat speaker.
FIGS. 10A and 10B are explanatory views showing a state in which a diaphragm of a flat speaker vibrates in a primary vibration mode, and FIG.
[Explanation of symbols]
10: yoke 10a: flat plate portion 10b: peripheral wall portion 10c: cylindrical portion 10d: annular recess 10e: cylindrical portion 12: permanent magnet 14: diaphragm 16: insulating sheet 18: voice coil 20: holding frame 26: opening 28: amplitude Suppression member 30: Damper 32: Trumpet-shaped support member 34: Solid block 36: Elastic bodies 38, 38A, 38B: Electromagnetic braking mechanism (amplitude suppression member)
40: support member 42: moving coil 44: magnetic circuit member 46: magnet 48: damper 52: first magnet 54: second magnet

Claims (14)

A yoke having a flat plate portion, a large number of permanent magnets attached to the flat plate portion of the yoke, a diaphragm provided with a voice coil corresponding to the permanent magnet on one or both sides of an insulating sheet, and the periphery of the diaphragm In a flat speaker provided with a holding frame that holds the portion so that a predetermined gap is formed between the diaphragm and the magnetic pole surface of the permanent magnet,
The vibration plate is allowed to vibrate at an amplitude that does not reach the magnetic pole face level of the permanent magnet at a location that vibrates at a relatively larger amplitude than other places, but at an amplitude that reaches the magnetic pole face level. A flat speaker comprising an amplitude suppressing member for suppressing vibration. 2. The flat speaker according to claim 1, wherein the amplitude suppressing member is provided in at least one of the positions corresponding to the center of the antinode of the low-order vibration mode lower than the third-order vibration mode of the diaphragm or the vicinity thereof. A characteristic flat speaker. 3. The flat speaker according to claim 1 or 2, wherein the amplitude suppressing member is configured to support the stationary diaphragm with a predetermined gap between it and the magnetic pole surface of the permanent magnet. A characteristic flat speaker. The flat speaker according to any one of claims 1 to 3, wherein the amplitude suppressing member has a concentric corrugated wave shape and a peripheral portion fixed to the yoke, and one end side of the central portion of the damper. And a support member having the other end fixed to the diaphragm. 5. The flat speaker according to claim 4, wherein the support member is a trumpet member or a cylindrical member. The flat speaker according to any one of claims 1 to 3, wherein the amplitude suppressing member includes a solid block fixed to the yoke and an elastic body attached to the solid block so as to support the diaphragm. A flat speaker characterized by being configured. 7. The flat speaker according to claim 6, wherein the solid block is the same as many permanent magnets attached to the yoke. 4. The flat speaker according to claim 1, wherein the amplitude suppressing member is constituted by an electromagnetic braking mechanism. 9. The flat speaker according to claim 8, wherein the electromagnetic braking mechanism applies a movable coil attached to the diaphragm via a support member so that the central axis is directed in the vibration direction, and applies a radial magnetic flux to the movable coil. And a magnet attached to the yoke. 10. The flat speaker according to claim 9, wherein the one-turn or multi-turn movable coil is in a short-circuit state between both terminals. The flat speaker according to claim 9, wherein the support member is integrated with a lightweight metal. 10. The flat speaker according to claim 9, wherein the movable coil has a driving force by causing a voice current to flow in a part thereof. 10. The flat speaker according to claim 9, wherein the support member is supported by the yoke via a damper. The flat speaker according to any one of claims 1 to 3, wherein the amplitude suppressing member is attached to the diaphragm so that the first magnet attached to the yoke and the same polarity as the magnet are opposed to each other. A flat speaker comprising two magnets.

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