JP2006086733A - Thin tweeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin type tweeter which obtains a desirable curve of pressure-frequency characteristics for reproducing high-pitched tones even though it is of a thin type. <P>SOLUTION: A thin film speaker comprises a vibration film 10 integrated with a coil 22, multiple-magnetized permanent magnet plates 12, 14 opposed on the vibration film, and a case 16 for holding them wherein they are combined to cross fluxes of the permanent magnet plates with the coil of the vibration film. The surface of the vibration film 10 has a sound radiating open structure having many air holes 24, 34 while the backside of the vibration film 10 is a closed structure with no air hole. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a tweeter that is a speaker for high-frequency range reproduction. More specifically, a vibration film integrally formed with a coil and a monolithic permanent magnet plate subjected to multipolar magnetization are arranged to face each other. The present invention relates to a thin tweeter having an electroacoustic transducer and having a closed structure on the back surface side of the vibration film, which exhibits good high-frequency reproduction characteristics.

  As is well known, speakers have various structures, and a cone type is generally used as an electromagnetic system. However, in recent years, thin speakers combining a permanent magnet and a diaphragm have been developed. As this type of thin speaker, a vibration film in which a coil is integrally formed on a flexible resin film, and a permanent magnet plate that is subjected to multipolar magnetization and is disposed opposite to both the front and back surfaces of the vibration film, A conductor pattern comprising a case for holding the permanent magnet plate, the permanent magnet plate having a parallel striped magnetization pattern in which N poles and S poles appear alternately in a strip shape, and the coil having a straight portion And a structure in which the diaphragm and the permanent magnet plate are combined so that the linear portion of the coil is located in the boundary region between the S pole and the N pole has been developed and partially put into practical use (Patent Document 1) reference).

  In such a thin speaker, the magnetic flux generated by the permanent magnet plate is linked to the coil of the diaphragm, and the interaction between the drive current flowing through the coil and the magnetic field of the permanent magnet plate causes almost the entire diaphragm to be perpendicular to the film surface. It is configured to vibrate in the direction and thereby generate sound waves.

  This type of conventional thin speaker can be thinned even if the diaphragm is enlarged due to its structure, and the periphery of the diaphragm is free from being fixed without being fixed, so it is faithful to the drive current. There is an advantage that a large reproduced sound is generated and the amplitude can be increased. In order to take advantage of these advantages, it has been designed and manufactured exclusively for the full range so that the sound pressure-frequency characteristics are good over the widest possible sound range. Ventilation holes are formed to provide an open structure that can emit sound in both directions, so that a sufficiently large acoustic energy can be emitted.

On the other hand, a speaker system having a flat sound pressure characteristic over a wide sound range as a whole by combining a plurality of types of speakers such as two-way or three-way is often configured, but particularly in applications such as combining with a thin display device, There is a need for a small and thin tweeter. However, in the conventional structure as described above, the sound pressure-frequency characteristics in the high sound range cannot be improved simply by reducing the size of the diaphragm. Further, it is difficult to reduce the thickness by using a conventional general cone type speaker.
JP-A-9-331596

  The problem to be solved by the present invention is to provide a thin tweeter that has a thin structure and can obtain a desired curve for sound pressure-frequency characteristics for high-frequency reproduction.

  The present invention relates to a vibration film in which a coil is integrally formed on a resin film having flexibility, a permanent magnet plate that is subjected to multipolar magnetization and is disposed to face the vibration film surface, the permanent magnet plate, In a thin speaker that has a case for holding the diaphragm and is combined so that the magnetic flux generated by the permanent magnet plate is linked to the coil of the diaphragm, the surface of the diaphragm has a number of ventilation holes and can emit sound. In contrast to the open structure, the back side of the diaphragm is a closed structure that does not have a vent hole.

  The inventors of the present invention are inventors of Patent Document 1 cited as the prior art. Thereafter, with respect to this type of thin speaker, an ultra-compact size that can be incorporated into a mobile phone from a tatami-sized super-large speaker combined with an A3 unit. Prototype research and practical application have been conducted up to speakers. During the development process, it was found that the sound pressure characteristic in the high sound range sharply and smoothly rises and a good tweeter characteristic appears by closing the vent on the back side. The present invention has been completed based on the knowledge of this phenomenon.

  More preferably, in the present invention, a vibration film in which a coil is integrally formed on a resin film having flexibility, and a permanent magnet plate that is subjected to multipolar magnetization and is disposed to face both the front and back surfaces of the vibration film. And a case for holding the permanent magnet plate and the vibration film, the permanent magnet plate has a parallel striped magnetization pattern in which N poles and S poles appear alternately in a strip shape, and the coil has a straight portion. In the thin speaker in which the diaphragm and the permanent magnet plate are combined so that the linear portion of the coil is located in the boundary region between the south pole and the north pole, the permanent film on the surface side of the diaphragm is provided. While the magnet plate and the case surface have a sound-released open structure having a large number of ventilation holes, the permanent magnet plate and / or the case surface on the back side of the vibration membrane has a closed structure without ventilation holes. A thin tweeter characterized by That. When the back side case surface has a closed structure that does not have a vent hole, a through hole may be formed in the back side permanent magnet plate. That is, both the front and back permanent magnet plates may have the same porous structure.

  The shape and material of the permanent magnet plate are arbitrary, and may be a sintered magnet or a metal magnet, but generally a plastic magnet containing ferrite or rare earth magnetic powder (such as Sm—Co or neodymium iron) is used. The vibration film is typically formed by printing and wiring a meandering (reciprocating) conductor pattern serving as a coil on one surface of a resin film. The linear portion of the coil located in the boundary region between the S pole and the N pole is not limited to one, but may be a state in which a plurality of coils are arranged in parallel (multiple meander pattern). Conductive patterns can also be formed on both sides of the resin film.

  In these, a cushioning sheet having air permeability and elasticity is interposed between the vibration film and the permanent magnet plate, and the periphery of the vibration film is not fixed by an adhesive or the like and is free (free state). Is preferred.

  Since the thin tweeter according to the present invention closes the back side of the diaphragm, the sound pressure is increased on the high sound range side, and good sound pressure-frequency characteristics as a tweeter can be obtained. In addition, it is basically a combination of a permanent magnet plate and a diaphragm, so it can be made thinner, and in the high sound range, the vibration amplitude of the diaphragm is very small, so the distance between the permanent magnet plate and the diaphragm can be narrowed. Also, the conversion efficiency of electromagnetic energy into acoustic energy is increased.

  In the present invention, since the periphery of the vibration film can be made free without being firmly fixed, a fulcrum does not occur in the peripheral portion, and a reproduced sound faithful to the high frequency range component of the coil drive current can be obtained. In addition, since the multi-pole magnetized permanent magnet plate having an integral structure is used, it can be manufactured easily and with high accuracy, and sufficient mechanical strength can be provided.

  An example of the optimum structure of the thin tweeter according to the present invention is shown in FIGS. FIG. 1 is an exploded perspective view, and FIG. 2 is an explanatory view of the outer appearance, showing a back surface (A) / front surface (B) / side surface (C).

  The thin tweeter according to the present invention mainly includes a vibration film 10 in which coils are integrally formed, and multi-pole magnetization, and both surfaces of the vibration film 10 are opposed to each other with a slight magnetic gap therebetween. Permanent magnet plates 12, 14 and a case 16 for holding the permanent magnet plates 12, 14 and the vibrating membrane 10. The magnetic flux generated by the permanent magnet plates 12, 14 is linked to the coil of the vibrating membrane 10. Are combined. As shown in the figure, the magnetic drive source in the present invention is a flat or sheet-like integrated (not separated) permanent magnet plate.

  The vibration film 10 is formed by integrally forming a meandering (reciprocating) conductor pattern serving as a coil 22 on one surface of a flexible resin film (for example, a polyimide resin film) 20 by a printed wiring technique. The permanent magnet plates 12 and 14 are, for example, Sm-Co plastic magnets and the like, and are parallel and symmetrical so as to have a parallel stripe-like magnetization pattern in which N and S poles appear alternately in a strip shape. Multipolar magnetization is applied to almost the entire surface with the same magnetic strength. The vibrating membrane 10 and the permanent magnet plates 12 and 14 are combined so that the linear portion of the coil 22 is spatially arranged in a completely centered manner with the boundary between the S pole and the N pole as the center line.

  The permanent magnet plate 12 located on the front side has a shape in which a large number of air holes 24 are formed in alignment in the boundary region between the south pole and the north pole. On the other hand, in this example, the permanent magnet plate 14 located on the back side has a shape without a vent hole.

  A buffer sheet 26 having air permeability and elasticity is interposed between the vibration membrane 10 and the permanent magnet plates 12 and 14, and the periphery of the vibration membrane 10 is not fixed and is free (free state). Yes. However, in the in-plane direction, particularly in the direction orthogonal to the linear portion of the coil, it is necessary to prevent positional deviation. In this example, a belt-like spacer 28 is provided on one side of the coil drawing side between the vibrating membrane 10 and the buffer sheet 26 and pressed (not firmly fixed with an adhesive or the like), and the remaining three sides are completely free. Yes. As the buffer sheet 26, for example, one or a plurality of nonwoven fabrics are used. The tweeter is for high-frequency range reproduction, and the vibration amplitude of the vibration film itself is very small, so that it is essentially unnecessary to interpose a buffer sheet. However, the buffer sheet can be interposed in this manner in order to prevent dust or protection and design / assembly. In this example, one side of the vibrating membrane 10 is pressed by the belt-like spacer 28, but the tweeter has no significant problem in practical characteristics. The coil end can be pulled out by bending the holding side.

  The case 16 is composed of a combination of a container-like case main body 30 located on the front side and a flat back cover 32. The case main body 30 is an integrally formed product obtained by punching and bending (or drawing) a metal plate (iron plate or the like), and its main surface passes through the same position as the vent hole 24 provided in the permanent magnet plate 12. A pore 34 is formed. The back cover 32 is also formed by punching a metal plate (such as an iron plate), and has a structure in which an attachment portion 36 is integrally formed on the outer periphery and an external terminal 38 (see FIG. 2) is provided on the back side. . Vent holes are not formed in the back cover 32. A plurality of claw portions 40 are formed in a distributed manner around the case body 30, and each of the claw portions 40 is bent on the back side in accordance with the notches 42 of the back cover 32, so that the vibrating membrane 10, the permanent magnet plates 12, 14, etc. Bond and fix in an enclosed state. Since the method of fixing the claw portion 40 by bending does not require a set screw or the like, it is preferable from the viewpoint of reducing the number of parts and the number of assembly steps. The coil terminal formed on the vibrating membrane 10 is connected to an external terminal 38 provided on the back side of the back cover 32.

  In the above example, both the permanent magnet plate and the back cover on the back side of the vibration membrane have a closed structure that does not have a vent hole. However, in the present invention, it is only necessary that the back surface side of the vibration film has a closed structure. If there is no vent hole in the back cover, the permanent magnet plate may have a vent hole. If the permanent magnet plate may have a vent hole, the same permanent magnet plate can be used on the front side and the back side, the number of parts can be reduced, and the amount of material can be reduced because the vent hole is formed.

  In addition, although the example shown in FIG. 1 is a flat plate structure, it can also be made into a curved structure in which the surface side is convex. The outer shape is not limited to a rectangle, but can be any shape. The structure of the case and the spacer can also be changed, and the frame-shaped spacer and both the front and back surfaces can be made of a flat magnet holding plate. In that case, the frame-shaped spacer serves as the side surface of the case and functions to prevent the vibration film from moving in the in-plane direction.

  FIG. 3 shows the results of measuring the sound pressure-frequency characteristics of the product (A) of the present invention in which only the back side is closed and the conventional structure (comparative example) (B) in which vent holes are formed in the same manner as the front and back sides. The outer shape of the thin tweeter used for the measurement is 53 mm in length, 39 mm in width, about 6 mm in thickness, excluding the mounting portion, and the input impedance is 4Ω. The characteristic diagram is a measurement result at 0 dB = 80 dB, 1 meter, and 1 W input.

  In the configuration of the comparative example (B), the sound pressure gradually rises from around 500 Hz and attempts to flatten on the higher frequency side than about 4 kHz, but fluctuates so as to be greatly undulated. On the other hand, in the configuration of the product (A) of the present invention, the sound pressure rises sharply and smoothly from around 2 kHz, and a good flat characteristic is obtained on the higher frequency side than about 8 kHz. Further, in the product of the present invention, the sound pressure in a high sound range of 8 kHz or higher is improved by 10 dB or more compared to the comparative example. Comparing both characteristic diagrams, it can be seen that the product of the present invention has extremely good characteristics as a tweeter.

The disassembled perspective view which shows an example of the thin tweeter which concerns on this invention. FIG. The graph which shows the sound pressure-frequency characteristic of this invention structure and a comparative example.

Explanation of symbols

10 Vibration membrane 12, 14 Permanent magnet plate 16 Case 24, 34 Vent

Claims (3)

A vibration film in which a coil is integrally formed on a flexible resin film, a permanent magnet plate that is subjected to multipolar magnetization and is disposed to face the vibration film surface, and holds the permanent magnet plate and the vibration film In a thin speaker that is combined so that the magnetic flux generated by the permanent magnet plate is linked to the coil of the diaphragm,
A thin tweeter characterized in that the surface side of the diaphragm has an open structure capable of sound emission having a large number of ventilation holes, whereas the back side of the diaphragm has a closed structure without ventilation holes. A vibration film in which a coil is integrally formed on a flexible resin film, a permanent magnet plate that is subjected to multipolar magnetization and is disposed opposite to the front and back surfaces of the vibration film, and the permanent magnet plate and vibration A permanent magnet plate having a parallel striped magnetization pattern in which N poles and S poles appear alternately in a strip shape, and a coil having a conductor pattern with straight portions; In the thin speaker in which the diaphragm and the permanent magnet plate are combined so that the linear portion of the coil is located in the boundary region between the S pole and the N pole,
The permanent magnet plate and the case surface on the surface side of the diaphragm have an open structure capable of emitting sound, and the permanent magnet plate and / or the case surface on the back side of the diaphragm have vent holes. A thin tweeter characterized by having a closed structure that does not have. The thin film according to claim 1 or 2, wherein a cushioning member having air permeability and elasticity is interposed between the vibration film and the permanent magnet plate, and the periphery of the vibration film is not fixed and most of it is in a free state. Tweeter.

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